# Javascript Reference - M to Q

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# Math

Object. A built-in object that has properties and methods for mathematical constants and functions. For example, the Math object's PI property has the value of pi.

### Syntax

To use a Math object:

```1. Math.propertyName
2. Math.methodName(parameters)```

### Parameters

propertyName is one of the properties listed below.

methodName is one of the methods listed below.

### Property of

None. The Math object is a top-level, built-in JavaScript object.

Navigator 2.0

### Description

You reference the constant PI as Math.PI. Constants are defined with the full precision of real numbers in JavaScript. Similarly, you reference Math functions as methods. For example, the sine function is Math.sin(argument), where argument is the argument.

It is often convenient to use the with statement when a section of code uses several Math constants and methods, so you don't have to type "Math" repeatedly. For example,

```with (Math) {
a = PI * r*r
y = r*sin(theta)
x = r*cos(theta)
}```

### Properties

The Math object has the following properties:
 E LN2 LN10 LOG2E LOG10E PI SQRT1_2 SQRT2

### Methods

The Math object has the following methods:
 abs acos asin atan atan2 ceil cos eval exp floor log max min pow random round sin sqrt tan toString valueOf

None.

### Examples

See the examples for the individual properties and methods.

# max

Method. Returns the greater of two numbers.

### Syntax

`Math.max(number1, number2)`

### Parameters

number1 and number2 are any numeric arguments or the properties of existing objects.

Math

Navigator 2.0

### Examples

The following function evaluates the variables x and y:

```function getMax(x,y) {
return Math.max(x,y)
}```
If you pass getMax the values 10 and 20, it returns 20; if you pass it the values -10 and -20, it returns -10.

min method

# MAX_VALUE

Property. The maximum numeric value representable in JavaScript.

### Syntax

`Number.MAX_VALUE`

Number

Navigator 3.0

No

### Description

The maximum numeric value representable in JavaScript

The MAX_VALUE property has a value of approximately 1.79E+308. Values larger than MAX_VALUE are represented as "Infinity".

Because MAX_VALUE is a constant, it is a read-only property of Number.

### Examples

The following code multiplies two numeric values. If the result is less than or equal to MAX_VALUE, the func1 function is called; otherwise, the func2 function is called.

```if (num1 * num2 <= Number.MAX_VALUE)
func1()
else
func2()```

MIN_VALUE, NaN, NEGATIVE_INFINITY, POSITIVE_INFINITY properties

# method

Property. A string specifying how form field input information is sent to the server.

### Syntax

`formName.method`

### Parameters

formName is either the name of a form or an element in the forms array.

Form object

Navigator 2.0

No

### Description

The method property is a reflection of the METHOD attribute of the <FORM> tag. The method property should evaluate to either "get" or "post."

You can set the method property at any time.

### Examples

The following function returns the value of the musicForm method property:

```function getMethod() {
return document.musicForm.method
}```

action, encoding, target properties; Form object

# MimeType

Object. A MIME type (Multipart Internet Mail Extension) supported by the client.

### Syntax

To use a MimeType object:

`navigator.mimeTypes[index].propertyName`

### Parameters

index is either an integer representing a MIME type supported by the client or a string containing the type of a MimeType object (from the type property).

propertyName is one of the properties listed below.

### Property of

The mimeTypes array is a property of navigator.

The MimeType object is a member of the mimeTypes array; each Plugin object also has an array of MimeType objects.

Navigator 3.0

### Description

Each MimeType object is an element in the mimeTypes array.

For example, the following table summarizes the values for displaying JPEG images:

Expression Value
navigator.mimeTypes["image/jpeg"].type image/jpeg
navigator.mimeTypes["image/jpeg"].description JPEG Image
navigator.mimeTypes["image/jpeg"].suffixes jpeg, jpg, jpe, jfif, pjpeg, pjp
navigator.mimeTypes["image/jpeg"].enabledPlugins null

#### The mimeTypes array

The mimeTypes array contains an entry for each MIME type supported by the client (either internally, via helper applications, or by plug-ins). For example, if a client supports three MIME types, these MIME types are reflected as navigator.mimeTypes[0], navigator.mimeTypes[1], and navigator.mimeTypes[2].

Each element of the mimeTypes array is a MimeType object.

To use the mimeTypes array:

```1. navigator.mimeTypes[index]
2. navigator.mimeTypes.length```
index is either an integer representing a MIME type supported by the client or a string containing the type of a MimeType object (from the type property).

To obtain the number of MIME types supported by the client, use the length property: navigator.mimeTypes.length.

Elements in the mimeTypes array are read-only. For example, the statement navigator.mimeTypes[0]="video/quicktime" has no effect.

#### The mimeTypes array used with the Plugin object

Each Plugin object has its own mimeTypes array, which contains an entry for each MIME type handled by the plug-in. For information, see Plugin.

### Properties

The MimeType object has the following properties:

Property Description
description A description of the type
enabledPlugin A reference to the Plugin object configured for the MIME type
type The name of the MIME type, for example "video/mpeg or audio/x-wav"
suffixes A string listing possible file name extensions for the MIME type, for example "mpeg, mpg, mpe, mpv, vbs, mpegv"

The mimeTypes array has the following properties:

Property Description
length Reflects the number of MIME types supported by the client

None.

### Examples

The following code displays the type, description, suffixes, and enabledPlugin properties for each MimeType object on a client:

```document.writeln("<TABLE BORDER=1><TR VALIGN=TOP>",
"<TH ALIGN=left>i",
"<TH ALIGN=left>type",
"<TH ALIGN=left>description",
"<TH ALIGN=left>suffixes",
"<TH ALIGN=left>enabledPlugin.name</TR>")
for (i=0; i < navigator.mimeTypes.length; i++) {
document.writeln("<TR VALIGN=TOP><TD>",i,
"<TD>",navigator.mimeTypes[i].type,
"<TD>",navigator.mimeTypes[i].description,
"<TD>",navigator.mimeTypes[i].suffixes)
if (navigator.mimeTypes[i].enabledPlugin==null) {
document.writeln(
"<TD>None",
"</TR>")
} else {
document.writeln(
"<TD>",navigator.mimeTypes[i].enabledPlugin.name,
"</TR>")
}
}
document.writeln("</TABLE>")```
The preceding example displays output similar to the following:

i type description suffixes enabledPlugin.name
0 audio/aiff AIFF  aif, aiff LiveAudio
1 audio/wav WAV  wav LiveAudio
2 audio/x-midi MIDI  mid, midi LiveAudio
3 audio/midi MIDI  mid, midi LiveAudio
4 video/msvideo Video for Windows  avi NPAVI32 Dynamic Link Library
5 * Netscape Default Plugin  Netscape Default Plugin
6 zz-application/zz-winassoc-TGZ TGZ None

Plugin object

# mimeTypes

Property. An array of all MIME types supported by the client. See the MimeType object for information.

No

# min

Method. Returns the lesser of two numbers.

### Syntax

`Math.min(number1, number2)`

### Parameters

number1 and number2 are any numeric arguments or the properties of existing objects.

Math

Navigator 2.0

### Examples

The following function evaluates the variables x and y:

```function getMin(x,y) {
return Math.min(x,y)
}```
If you pass getMin the values 10 and 20, it returns 10; if you pass it the values -10 and -20, it returns -20.

max method

# MIN_VALUE

Property. The smallest positive numeric value representable in JavaScript.

### Syntax

`Number.MIN_VALUE`

Number

Navigator 3.0

No

### Description

The MIN_VALUE property is the number closest to zero, not the most negative number, that JavaScript can represent.

MIN_VALUE has a value of approximately 2.22E-308. Values smaller than MIN_VALUE ("underflow values") are converted to zero.

Because MIN_VALUE is a constant, it is a read-only property of Number.

### Examples

The following code divides two numeric values. If the result is greater than or equal to MIN_VALUE, the func1 function is called; otherwise, the func2 function is called.

```if (num1 / num2 >= Number.MIN_VALUE)
func1()
else
func2()```

MAX_VALUE, NaN, NEGATIVE_INFINITY, POSITIVE_INFINITY properties

Navigator 2.0

# name

Property. A string specifying the name of an object.

### Syntax

```1. objectName.name
2. frameReference.name
3. frameReference.frames.name
5. imageName.name
6. navigator.plugins[index].name
7. windowReference.name
8. windowReference.frames.name```

### Parameters

objectName is either the value of the NAME attribute of any of the objects listed below or an element in the elements array.

frameReference is a valid way of referring to a frame, as described in the Frame object.

radioName is the value of the NAME attribute of a Radio object.

selectName is either the value of the NAME attribute of a Select object or an element in the elements array.

imageName is either the value of the NAME attribute of a Image object or an element in the images array.

index is either an integer representing a plug-in installed on the client or a string containing the name of a Plugin object (from the name property).

windowReference is a valid way of referring to a window, as described in the window object.

### Property of

Button object, Checkbox object, FileUpload object, Form object, Frame object, Hidden object, Image object, Password object, Plugin object, Radio object, Reset object, Select object, Submit object, Text object, Textarea object, window object

### Implemented in

• Navigator 2.0
• Navigator 3.0: property of FileUpload, Form, Image, and Plugin objects

Yes

### Description

The value of the name property differs between the window object and other objects. The name property is a read-only property for the FileUpload object, Image object, and Plugin object.

#### window object

The name property for the window object is represented by form 7 and form 8 of the syntax. The name property represents the value of the windowName argument described in the window object syntax. Both forms of the syntax represent the same value.

name is a read-only property.

#### Image and Plugin objects

The name property for Image and Plugin objects is represented by forms 5-6 of the syntax.

• For Image objects, the name property represents the value of the NAME attribute. For images created with the Image() constructor, the value of the name property is null.
• For Plugin objects, the name property is the plug-in's name and is supplied by the plug-in itself. Each plug-in should have a name that uniquely identifies it.
name is a read-only property.

#### All other objects

The name property for all other objects is represented by forms 1 through 4 of the syntax. For all objects except Image, Plugin, and window, the name property initially reflects the value of the NAME attribute. Changing the name property overrides this setting.

You can set the name property at any time.

The name property is the same for every radio button in a single Radio object. Individual radio buttons are referenced by their position in the Radio array.

Do not confuse the name property with the label displayed on a Button, Reset, or Submit object. The value property specifies the label for these objects. The name property is not displayed on-screen; it is used to reference the objects programmatically.

For a Frame object, the values specified by forms 1, 2, and 3 of the syntax are the same.

If multiple objects on the same form have the same NAME attribute, an array of the given name is created automatically. Each element in the array represents an individual Form object. Elements are indexed in source order starting at zero. For example, if two text elements and a textarea element on the same form have their NAME attribute set to "myField," an array with the elements myField[0], myField[1], and myField[2] is created.

### Examples

In the following example, the valueGetter function uses a for loop to iterate over the array of elements on the valueTest form. The msgWindow window displays the names of all the elements on the form:

```newWindow=window.open("http://home.netscape.com")

function valueGetter() {
var msgWindow=window.open("")
for (var i = 0; i < newWindow.document.valueTest.elements.length; i++) {
msgWindow.document.write(newWindow.document.valueTest.elements[i].name + "<BR>")
}
}```
In the following example, the first statement creates a window called netscapeWin. The second statement displays the value "netscapeHomePage" in the Alert dialog box, because "netscapeHomePage" is the value of the windowName argument of netscapeWin.

```netscapeWin=window.open("http://home.netscape.com","netscapeHomePage")

For Plugin objects, see the examples for the Plugin object.

For button, reset, and submit: value property

For Plugin: description, filename, length properties

# NaN

Property. A special value representing Not-A-Number. This value is represented as the unquoted literal NaN.

### Syntax

`Number.NaN`

Number

### Implemented in

Navigator 3.0

No

### Description

JavaScript prints the value Number.NaN as NaN.

NaN always compares unequal to any other number, including NaN itself; you cannot check for the not-a-number value by comparing to Number.NaN. Use the isNaN function insead.

You might use the NaN property to indicate an error condition for a function that should return a valid number.

Because NaN is a constant, it is a read-only property of Number.

### Examples

In the following example, if month has a value greater than 12, it is assigned NaN, and a message is displayed indicating valid values.

```var month = 13
if (month < 1 || month > 12) {
month = Number.NaN
alert("Month must be between 1 and 12.")
}```

MAX_VALUE, MIN_VALUE, NEGATIVE_INFINITY, POSITIVE_INFINITY properties; isNaN, parseFloat, parseInt functions

# navigator

Object. Contains information about the version of Navigator in use.

### Syntax

To use a navigator object:

```1. navigator.propertyName
2. navigator.methodName```

### Parameters

propertyName is one of the properties listed below.

methodName is one of the methods listed below.

None

### Implemented in

• Navigator 2.0
• Navigator 3.0: added mimeTypes, plugins properties; added javaEnabled method

### Description

Use the navigator object to determine which version of the Navigator your users have, what MIME types the user's Navigator can handle, and what plug-ins the user has installed.

### Properties

The navigator object has the following properties:

Property Description
appCodeName Specifies the code name of the browser
appName Specifies the name of the browser
appVersion Specifies version information for the Navigator
mimeTypes An array of all MIME types supported by the client
plugins An array of all plug-ins currently installed on the client
userAgent Specifies the user-agent header

### Methods

The navigator object has the following methods:
 eval javaEnabled taintEnabled toString valueOf

None.

### Examples

See the examples for the individual properties and methods.

# NEGATIVE_INFINITY

Property. A special numeric value representing negative infinity. This value is represented as "-Infinity".

### Syntax

`Number.NEGATIVE_INFINITY`

Number

### Implemented in

Navigator 3.0

No

### Description

This value behaves mathematically like an infinity; for example, anything multiplied by infinity is infinity, and anything divided by infinity is zero.

Because NEGATIVE_INFINITY is a constant, it is a read-only property of Number.

### Examples

In the following example, the variable smallNumber is assigned a value that is smaller than the minimum value. When the if statement executes, smallNumber has the value "-Infinity", so the func1 function is called.

```var smallNumber = -Number.MAX_VALUE*10
if (smallNumber == Number.NEGATIVE_INFINITY)
func1()
else
func2()```

MAX_VALUE, MIN_VALUE, NaN, POSITIVE_INFINITY properties

# next

Property. A string specifying the complete URL of the next history entry.

### Syntax

`history.next`

### Property of

history object

### Implemented in

Navigator 3.0

Yes

### Description

The next property reflects the URL that would be used if the user chose Forward from the Go menu. This property has a value only if data tainting is enabled; if data tainting is not enabled, next has no value.

next is a read-only property.

### Examples

The following example determines whether history.next contains the string "NETSCAPE.COM". If it does, the function myFunction is called.

```if (history.next.indexOf("NETSCAPE.COM") != -1) {
myFunction(history.next)
}```

current, previous properties; "Using data tainting for security"

# Number

Object. Lets you work with numeric values. The Number object is an object wrapper for primitive numeric values.

### Syntax

To create a Number object:

`numberObjectName = new Number()`
To use a Number object:

`numberObjectName.propertyName`

### Parameters

numberObjectName is either the name of a new object or a property of an existing object. When using Number properties, numberObjectName is either the name of an existing Number object or a property of an existing object.

propertyName is one of the properties listed below.

None

### Implemented in

Navigator 3.0

### Description

The Number object is a built-in JavaScript object.

The primary uses for the Number object are:

• To access its constant properties, which represent the largest and smallest representable numbers, positive and negative infinity, and the Not-a-Number value.
• To create numeric objects that you can add properties to. Most likely, you will rarely need to create a Number object.

### Properties

The Number object has the following properties:

Property Description
MAX_VALUE The largest representable number
MIN_VALUE The smallest representable number
NaN Special "not a number" value
NEGATIVE_INFINITY Special infinite value; returned on overflow
POSITIVE_INFINITY Special negative infinite value; returned on overflow
prototype Lets you add a properties to a Number object.

None.

### Examples

Example 1. The following example uses the Number object's properties to assign values to several numeric variables:

```biggestNum = Number.MAX_VALUE
smallestNum = Number.MIN_VALUE
infiniteNum = Number.POSITIVE_INFINITY
negInfiniteNum = Number.NEGATIVE_INFINITY
notANum = Number.NaN```
Note that these properties are properties of the Number() constructor itself, not of individual Number objects.

Example 2. The following example creates a Number object, myNum, then adds a description property to all Number objects. Then a value is assigned to the myNum object's description property.

```myNum = new Number(65)
Number.prototype.description=null
myNum.description="wind speed"```

# onAbort

Event handler. An abort event occurs when the user aborts the loading of an image (for example by clicking a link or clicking the Stop button). The onAbort event handler executes JavaScript code when an abort event occurs.

See the relevant objects for the onAbort syntax.

Image

### Implemented in

Navigator 3.0

### Examples

In the following example, an onAbort handler in an Image object displays a message when the user aborts the image load:

```<IMG NAME="aircraft" SRC="f15e.gif"
onAbort="alert('You didn\'t get to see the image!')">```

onError, onLoad event handlers

# onBlur

Event handler. A blur event occurs when a form element loses focus or when a window or frame loses focus. The blur event can result from a blur method or from the user clicking the mouse on another object or window or tabbing with the keyboard. The onBlur event handler executes JavaScript code when a blur event occurs.

For windows, frames, and framesets, the onBlur event handler specifies JavaScript code to execute when a window loses focus.

A frame's onBlur event handler overrides an onBlur event handler in the <BODY> tag of the document loaded into frame.

Note
On some platforms, placing an onBlur event handler in a <FRAMESET> tag has no effect. Please see the release notes (after starting Netscape, choose Release Notes from the Help menu).
See the relevant objects for the onBlur syntax.

### Event handler of

Button object, Checkbox object, FileUpload object, Frame object, Password object, Radio object, Reset object, Select object, Submit object, Text object, Textarea object, window object

### Implemented in

• Navigator 2.0
• Navigator 3.0: event handler of Button, Checkbox, FileUpload, Frame, Password, Radio, Reset, Submit, and window

### Examples

Example 1: Validate form input. In the following example, userName is a required text field. When a user attempts to leave the field, the onBlur event handler calls the required function to confirm that userName has a legal value.

`<INPUT TYPE="text" VALUE="" NAME="userName" onBlur="required(this.value)">`
Example 2: Change the background color of a window. In the following example, a window's onBlur and onFocus event handlers change the window's background color depending on whether the window has focus.

```<BODY BGCOLOR="lightgrey"
onBlur="document.bgColor='lightgrey'"
onFocus="document.bgColor='antiquewhite'">```
Example 3: Change the background color of a frame. The following example creates four frames. The source for each frame, onblur2.html has the <BODY> tag with the onBlur and onFocus event handlers shown in Example 1. When the document loads, all frames are "lightgrey". When the user clicks a frame, the onFocus event handler changes the frame's background color to "antiquewhite". The frame that loses focus is changed to "lightgrey". Note that the onBlur and onFocus event handlers are within the <BODY> tag, not the <FRAME> tag.

```<FRAMESET ROWS="50%,50%" COLS="40%,60%">
<FRAME SRC=onblur2.html NAME="frame1">
<FRAME SRC=onblur2.html NAME="frame2">
<FRAME SRC=onblur2.html NAME="frame3">
<FRAME SRC=onblur2.html NAME="frame4">
</FRAMESET>```
The following code has the same effect as the previous code, but is implemented differently. The onFocus and onBlur event handlers are associated with the frame, not the document. The onBlur and onFocus event handlers for the frame are specified by setting the onblur and onfocus properties. For information on using new to specify a string of JavaScript code to be compiled as a function, see the Function object.

```<SCRIPT>
function setUpHandlers() {
for (var i = 0; i < frames.length; i++) {
frames[i].onfocus=new Function("document.bgColor='antiquewhite'")
frames[i].onblur=new Function("document.bgColor='lightgrey'")
}
}
</SCRIPT>

<FRAMESET ROWS="50%,50%" COLS="40%,60%" onLoad=setUpHandlers()>
<FRAME SRC=onblur2.html NAME="frame1">
<FRAME SRC=onblur2.html NAME="frame2">
<FRAME SRC=onblur2.html NAME="frame3">
<FRAME SRC=onblur2.html NAME="frame4">
</FRAMESET>```
Example 4: Close a window. In the following example, a window's onBlur event handler closes the window when the window loses focus.

```<BODY onBlur="window.close()">
This is some text
</BODY>```

onChange, onFocus event handlers

# onChange

Event handler. A change event occurs when a select, text, or textarea field loses focus and its value has been modified. The onChange event handler executes JavaScript code when a change event occurs.

Use the onChange event handler to validate data after it is modified by a user.

See the relevant objects for the onChange syntax.

### Event handler of

FileUpload object, Select object, Text object, Textarea object

### Implemented in

• Navigator 2.0
• Navigator 3.0: event handler of FileUpload

### Examples

In the following example, userName is a text field. When a user changes the text and leaves the field, the onChange event handler calls the checkValue function to confirm that userName has a legal value.

`<INPUT TYPE="text" VALUE="" NAME="userName"    onChange="checkValue(this.value)">`

onBlur, onFocus event handlers

# onClick

Event handler. A click event occurs when an object on a form is clicked. The onClick event handler executes JavaScript code when a click event occurs.

For checkboxes, links, radio buttons, reset buttons, and submit buttons, the onClick event handler can return false to cancel the action normally associated with a click event.

For example, the following code creates a hyperlink that, when clicked, displays a confirm dialog box. If the user clicks the hyperlink and then chooses cancel, the page specified by the hyperlink is not loaded.

```<A HREF = "http://home.netscape.com/"
Returning false in an onClick event handler for a button has no effect.

Note
On some platforms, returning false in an onClick event handler for a reset button has no effect. Please see the release notes (after starting Netscape, choose Release Notes from the Help menu).
See the relevant objects for the onClick syntax.

### Event handler of

Button object, Checkbox object, Link object, Radio object, Reset object, Submit object

### Implemented in

• Navigator 2.0
• Navigator 3.0: added the ability to return false to cancel the action associated with a click event

### Examples

Example 1: Call a function when a user clicks a button. Suppose you have created a JavaScript function called compute. You can execute the compute function when the user clicks a button by calling the function in the onClick event handler, as follows:

`<INPUT TYPE="button" VALUE="Calculate" onClick="compute(this.form)">`
In the preceding example, the keyword this refers to the current object; in this case, the Calculate button. The construct this.form refers to the form containing the button.

For another example, suppose you have created a JavaScript function called pickRandomURL that lets you select a URL at random. You can use the onClick event handler of a link to specify a value for the HREF attribute of the <A> tag dynamically, as shown in the following example:

```<A HREF=""
onClick="this.href=pickRandomURL()"
onMouseOver="window.status='Pick a random URL'; return true">
Go!</A>```
In the above example, the onMouseOver event handler specifies a custom message for the Navigator status bar when the user places the mouse pointer over the Go! anchor. As this example shows, you must return true to set the window.status property in the onMouseOver event handler.

Example 2: Cancel the checking of a checkbox. The following example creates a checkbox with an onClick event handler. The event handler displays a confirm that warns the user that checking the checkbox purges all files. If the user chooses Cancel, the onClick event handler returns false and the checkbox is not checked.

```<INPUT TYPE="checkbox" NAME="check1" VALUE="check1"
onClick="return confirm('This purges all your files. Are you sure?')"> Remove files```

# onError

Event handler. An error event occurs when the loading of a document or image causes an error. The onError event handler executes JavaScript code when an error event occurs.

An error event occurs only when a JavaScript syntax or runtime error occurs, not when a Navigator error occurs. For example, if you try set window.location.href='notThere.html' and notThere.html does not exist, the resulting error message is a Navigator error message; therefore, an onError event handler would not intercept that message. However, an error event is triggered by a bad URL within an <IMG> tag or by corrupted image data.

window.onerror applies only to errors that occur in the window containing window.onerror, not in other windows.

The onError event handler can be any of the following:

• null to suppress all JavaScript error dialogs. Setting window.onerror to null means your users won't see JavaScript errors caused by your own code.
• The name of a function that handles errors (arguments are message text, URL, and line number of the offending line). To suppress the standard JavaScript error dialog, the function must return true. See Example 3 below.
• A variable or property that contains null or a valid function reference.
If you write an error-handling function, you have three options for reporting errors:

• Trace errors but let the standard JavaScript dialog report them (use an error handling function that returns false or does not return a value)
• Report errors yourself and disable the standard error dialog (use an error handling function that returns true)
• Turn off all error reporting (set the onError event handler to null)
See the relevant objects for the onError syntax.

### Event handler of

Image object, window object

### Implemented in

Navigator 3.0

### Examples

Example 1: Null event handler. In the following <IMG> tag, the code onError="null" suppresses error messages if errors occur when the image loads.

```<IMG NAME="imageBad1" SRC="corrupt.gif" ALIGN="left" BORDER="2"
onError="null">```
Example 2: Null event handler for a window. The onError event handler for windows cannot be expressed in HTML. Therefore, you must spell it all lowercase and set it in a <SCRIPT> tag. The following code assigns null to the onError handler for the entire window, not just the Image object. This suppresses all JavaScript error messages, including those for the Image object.

```<SCRIPT>
window.onerror=null
</SCRIPT>
<IMG NAME="imageBad1" SRC="corrupt.gif" ALIGN="left" BORDER="2">```
However, if the Image object has a custom onError event handler, the handler would execute if the image had an error. This is because window.onerror=null suppresses JavaScript error messages, not onError event handlers.

```<SCRIPT>
window.onerror=null
function myErrorFunc() {
}
</SCRIPT>
<IMG NAME="imageBad1" SRC="corrupt.gif" ALIGN="left" BORDER="2"
onError="myErrorFunc()">```
In the following example, window.onerror=null suppresses all error reporting. Without onerror=null, the code would cause a stack overflow error because of infinite recursion.

```<SCRIPT>
window.onerror = null;
function testErrorFunction() {
testErrorFunction();
}
</SCRIPT>
test message
</BODY>```
Example 3: Error handling function. The following example defines a function, myOnError, that intercepts JavaScript errors. The function uses three arrays to store the message, URL, and line number for each error. When the user clicks the Display Error Report button, the displayErrors function opens a window and creates an error report in that window. Note that the function returns true to suppress the standard JavaScript error dialog.

```<SCRIPT>
window.onerror = myOnError

msgArray = new Array()
urlArray = new Array()
lnoArray = new Array()

function myOnError(msg, url, lno) {
msgArray[msgArray.length] = msg
urlArray[urlArray.length] = url
lnoArray[lnoArray.length] = lno
return true
}

function displayErrors() {
win2=window.open('','window2','scrollbars=yes')
win2.document.writeln('<B>Error Report</B><P>')

for (var i=0; i < msgArray.length; i++) {
win2.document.writeln('<B>Error in file:</B> ' + urlArray[i] + '<BR>')
win2.document.writeln('<B>Line number:</B> ' + lnoArray[i] + '<BR>')
win2.document.writeln('<B>Message:</B> ' + msgArray[i] + '<P>')
}
win2.document.close()
}
</SCRIPT>

<FORM>
<BR><INPUT TYPE="button" VALUE="This button has a syntax error"

<P><INPUT TYPE="button" VALUE="Display Error Report"
onClick="displayErrors()">
</FORM>```
This example produces the following output:

`Error Report`
```Error in file: file:///c%7C/temp/onerror.html
Line number: 34
Message: unterminated string literal```
```Error in file: file:///c%7C/temp/onerror.html
Line number: 34
Message: missing ) after argument list```
```Error in file: file:///c%7C/temp/onerror.html
Line number: 30
Message: noSuchFunction is not defined```
Example 4: Event handler calls a function. In the following <IMG> tag, the onError event handler calls the function badImage if errors occur when the image loads.

```<SCRIPT>
alert('Error: ' + theImage.name + ' did not load properly.')
}
</SCRIPT>
<FORM>
<IMG NAME="imageBad2" SRC="orca.gif" ALIGN="left" BORDER="2"
</FORM>```

onAbort, onLoad event handlers

# onFocus

Event handler. A focus event occurs when a window, frame, or frameset receives focus or when a form element receives input focus. The focus event can result from a focus method or from the user clicking the mouse on an object or window or tabbing with the keyboard. Selecting within a field results in a select event, not a focus event. The onFocus event handler executes JavaScript code when a focus event occurs.

A frame's onFocus event handler overrides an onFocus event handler in the <BODY> tag of the document loaded into frame.

Note that placing an alert in an onFocus event handler results in recurrent alerts: when you press OK to dismiss the alert, the underlying window gains focus again and produces another focus event.

Note
On some platforms, placing an onFocus event handler in a <FRAMESET> tag has no effect. Please see the release notes (after starting Netscape, choose Release Notes from the Help menu).
See the relevant objects for the onFocus syntax.

### Event handler of

Button object, Checkbox object, FileUpload object, Frame object, Password object, Radio object, Reset object, Select object, Submit object, Text object, Textarea object, window object

### Implemented in

• Navigator 2.0
• Navigator 3.0: event handler of Button, Checkbox, FileUpload, Frame, Password, Radio, Reset, Submit, and window

### Examples

The following example uses an onFocus handler in the valueField Textarea object to call the valueCheck function.

`<INPUT TYPE="textarea" VALUE="" NAME="valueField" onFocus="valueCheck()">`
See also the examples for the onBlur event handler.

onBlur, onChange event handlers

Event handler. A load event occurs when Navigator finishes loading a window or all frames within a <FRAMESET> tag. The onLoad event handler executes JavaScript code when a load event occurs.

Use the onLoad event handler within either the BODY or the <FRAMESET> tag, for example, <BODY onLoad="...">.

In a FRAMESET and FRAME relationship, an onLoad event within a frame (placed in the <BODY> tag) occurs before an onLoad event within the FRAMESET (placed in the <FRAMESET> tag).

For images, the onLoad event handler indicates the script to execute when an image is displayed. Do not confuse displaying an image with loading an image. You can load several images, then display them one by one in the same Image object by setting the object's src property. If you change the image displayed in this way, the onLoad event handler executes every time an image is displayed, not just when the image is loaded into memory.

If you specify an onLoad event handler for an Image object that displays a looping GIF animation (multi-image GIF), each loop of the animation triggers the onLoad event, and the event handler executes once for each loop.

You can use the onLoad event handler to create a JavaScript animation by repeatedly setting the src property of an Image object. See the Image object for information.

### Event handler of

Image object, window object

### Implemented in

• Navigator 2.0
• Navigator 3.0: event handler of Image

### Examples

Example 1: Display message when page loads. In the following example, the onLoad event handler displays a greeting message after a Web page is loaded.

`<BODY onLoad="window.alert("Welcome to the Brave New World home page!")>`
Example 2: Display alert when image loads. The following example creates two Image objects, one with the Image() constructor and one with the <IMG> tag. Each Image object has an onLoad event handler that calls the displayAlert function, which displays an alert. For the image created with the <IMG> tag, the alert displays the image name. For the image created with the Image() constructor, the alert displays a message without the image name. This is because the onLoad handler for an object created with the Image() constructor must be the name of a function, and it cannot specify parameters for the displayAlert function.

```<SCRIPT>
imageA = new Image(50,50)
imageA.src="cyanball.gif"

if (theImage==null) {
}
else alert(theImage.name + ' has been loaded.')
}
</SCRIPT>

<IMG NAME="imageB" SRC="greenball.gif" ALIGN="top"
Example 3: Looping GIF animation. The following example displays an image, birdie.gif, that is a looping GIF animation. The onLoad event handler for the image increments the variable cycles, which keeps track of the number of times the animation has looped. To see the value of cycles, the user clicks the button labeled Count Loops.

```<SCRIPT>
var cycles=0
</SCRIPT>
<IMG ALIGN="top" SRC="birdie.gif" BORDER=0
<INPUT TYPE="button" VALUE="Count Loops"
onClick="alert('The animation has looped ' + cycles + ' times.')">```
Example 4: Change GIF animation displayed. The following example uses an onLoad event handler to rotate the display of six GIF animations. Each animation is displayed in sequence in one Image object. When the document loads, !anim0.html is displayed. When that animation completes, the onLoad event handler causes the next file, !anim1.html, to load in place of the first file. After the last animation, !anim5.html, completes, the first file is again displayed. Notice that the changeAnimation function does not call itself after changing the src property of the Image object. This is because when the src property changes, the image's onLoad event handler is triggered and the changeAnimation function is called.

```<SCRIPT>
var whichImage=0
var maxImages=5

function changeAnimation(theImage) {
++whichImage
if (whichImage <= maxImages) {
var imageName="!anim" + whichImage + ".gif"
theImage.src=imageName
} else {
whichImage=-1
return
}
}
</SCRIPT>

<IMG NAME="changingAnimation" SRC="!anim0.gif" BORDER=0 ALIGN="top"
See also the examples for the Image object.

onAbort, onError, onUnload event handlers

# onMouseOut

Event handler. A mouseOut event occurs each time the mouse pointer leaves an area (client-side image map) or link from inside that area or link. The onMouseOut event handler executes JavaScript code when a mouseOut event occurs.

If the mouse moves from one area into another in a client-side image map, you'll get onMouseOut for the first area, then onMouseOver for the second.

Area objects that use the onMouseOut event handler must include the HREF attribute within the <AREA> tag.

You must return true within the event handler if you want to set the status or defaultStatus properties with the onMouseOver event handler.

See the relevant objects for the onMouseOut syntax.

### Event handler of

Area object (see Link object), Link object

### Implemented in

Navigator 3.0

### Examples

See the examples for the Link object.

onMouseOver event handler

# onMouseOver

Event handler. A mouseOver event occurs once each time the mouse pointer moves over an object or area from outside that object or area. The onMouseOver event handler executes JavaScript code when a mouseOver event occurs.

If the mouse moves from one area into another in a client-side image map, you'll get onMouseOut for the first area, then onMouseOver for the second.

Area objects that use the onMouseOver event handler must include the HREF attribute within the <AREA> tag.

You must return true within the event handler if you want to set the status or defaultStatus properties with the onMouseOver event handler.

See the relevant objects for the onMouseOver syntax.

### Event handler of

Area object (see Link object), Link object

### Implemented in

• Navigator 2.0
• Navigator 3.0: event handler of Area

### Examples

By default, the HREF value of an anchor displays in the status bar at the bottom of the Navigator when a user places the mouse pointer over the anchor. In the following example, the onMouseOver event handler provides the custom message "Click this if you dare."

```<A HREF="http://home.netscape.com/"
onMouseOver="window.status='Click this if you dare!'; return true">
Click me</A>```
See onClick for an example of using onMouseOver when the <A> tag's HREF attribute is set dynamically.

onMouseOut event handler

# onReset

Event handler. A reset event occurs when a user resets a form (clicks a Reset button). The onReset event handler executes JavaScript code when a reset event occurs.

See the relevant objects for the onReset syntax.

Form object

### Implemented in

Navigator 3.0

### Examples

The following example displays a Text object with the default value "CA" and a reset button. If the user types a state abbreviation in the Text object and then clicks the reset button, the original value of "CA" is restored. The form's onReset event handler displays a message indicating that defaults have been restored.

```<FORM NAME="form1" onReset="alert('Defaults have been restored.')">
State:
<INPUT TYPE="text" NAME="state" VALUE="CA" SIZE="2"><P>
<INPUT TYPE="reset" VALUE="Clear Form" NAME="reset1">
</FORM>```

reset method, Reset object

# onSelect

Event handler. A select event occurs when a user selects some of the text within a text or textarea field. The onSelect event handler executes JavaScript code when a select event occurs.

See the relevant objects for the onSelect syntax.

### Event handler of

Text object, Textarea object

### Implemented in

Navigator 2.0

### Examples

The following example uses an onSelect handler in the valueField Text object to call the selectState function.

`<INPUT TYPE="text" VALUE="" NAME="valueField" onSelect="selectState()">`

# onSubmit

Event handler. A submit event occurs when a user submits a form. The onSubmit event handler executes JavaScript code when a submit event occurs.

You can use the onSubmit event handler to prevent a form from being submitted; to do so, put a return statement that returns false in the event handler. Any other returned value lets the form submit. If you omit the return statement, the form is submitted.

See the relevant objects for the onSubmit syntax.

Form object

### Implemented in

Navigator 2.0

### Examples

In the following example, the onSubmit event handler calls the validate function to evaluate the data being submitted. If the data is valid, the form is submitted; otherwise, the form is not submitted.

```<FORM onSubmit="return validate(this)">
...
</FORM>```
See also the examples for the Form object.

Submit object, submit method

Event handler. An unload event occurs when you exit a document. The onUnload event handler executes JavaScript code when an unload event occurs.

Use the onUnload event handler within either the BODY or the <FRAMESET> tag, for example, <BODY onUnload="...">.

In a frameset and frame relationship, an onUnload event within a frame (placed in the <BODY> tag) occurs before an onUnload event within the frameset (placed in the <FRAMESET> tag).

### Event handler of

window object

### Implemented in

Navigator 2.0

### Examples

In the following example, the onUnload event handler calls the cleanUp function to perform some shutdown processing when the user exits a Web page:

`<BODY onUnload="cleanUp()">`

# open (document object)

Method. Opens a stream to collect the output of write or writeln methods.

### Syntax

```document.open(["mimeType"])
[windowReference.]document.open("text/html","replace")```

### Parameters

mimeType is an optional argument that specifies the type of document to which you are writing. If you do not specify a mimeType, text/html is the default.

• text/html specifies a document containing ASCII text with HTML formatting.
• text/plain specifies a document containing plain ASCII text with end-of-line characters to delimit displayed lines.
• image/gif specifies a document with encoded bytes constituting a GIF header and pixel data.
• image/jpeg specifies a document with encoded bytes constituting a JPEG header and pixel data.
• image/x-bitmap specifies a document with encoded bytes constituting a bitmap header and pixel data.
• plugIn loads the specified plug-in and uses it as the destination for write and writeln methods. For example, "x-world/vrml" loads the VR Scout VRML plug-in from Chaco Communications, and "application/x-director" loads the Macromedia Shockwave plug-in. Plug-in MIME types are only valid if the user has installed the required plug-in software.
windowReference is a valid way of referring to a window, as described in the window object.

"replace" causes the new document to reuse the history entry that the previous document used. When you specify "replace" while opening a document, the target window's history length is not incremented even after you write and close.

document

### Implemented in

• Navigator 2.0
• Navigator 3.0: added "replace" parameter; document.open() or document.open("text/html") clears the current document if it has finished loading

### Description

The open method opens a stream to collect the output of write or writeln methods. If the mimeType is text or image, the stream is opened to layout; otherwise, the stream is opened to a plug-in. If a document exists in the target window, the open method clears it.

End the stream by using the document.close() method. The close method causes text or images that were sent to layout to display. After using document.close(), issue document.open() again when you want to begin another output stream.

In Navigator 3.0, document.open() or document.open("text/html") clears the current document if it has finished loading. This is because this type of open call writes a default <BASE HREF=> tag so you can generate relative URLs based on the generating script's document base.

#### Using "replace"

The "replace" keyword causes the new document to reuse the history entry that the previous document used. When you specify "replace" while opening a document, the target window's history length is not incremented even after you write and close.

"replace" is typically used on a window that has a blank document or an "about:blank" URL. After "replace" is specified, the write method typically generates HTML for the window, replacing the history entry for the blank URL. Take care when using generated HTML on a window with a blank URL. If you do not specify "replace", the generated HTML has its own history entry, and the user can press the Back button and back up until the frame is empty.

After document.open("text/html","replace") executes, history.current for the target window is the URL of document that executed document.open.

### Examples

Example 1. The following function calls document.open to open a stream before issuing a write method:

```function windowWriter1() {
var myString = "Hello, world!"
msgWindow.document.open()
msgWindow.document.write("<P>" + myString)
msgWindow.document.close()
}```
Example 2. The following function calls document.open with the "replace" keyword to open a stream before issuing write methods. The HTML code in the write methods is written to msgWindow, replacing the current history entry. The history length of msgWindow is not incremented.

```function windowWriter2() {
var myString = "Hello, world!"
msgWindow.document.open("text/html","replace")
msgWindow.document.write("<P>" + myString)
msgWindow.document.write("<P>history.length is " +
msgWindow.history.length)
msgWindow.document.close()
}```
The following code creates the msgWindow window and calls the function:

```msgWindow=window.open('','',
'toolbar=yes,scrollbars=yes,width=400,height=300')
windowWriter2()```
Example 3. In the following example, the probePlugIn function determines whether a user has the Shockwave plug-in installed:

```function probePlugIn(mimeType) {
var havePlugIn = false
var tiny = window.open("", "teensy", "width=1,height=1")
if (tiny != null) {
if (tiny.document.open(mimeType) != null)
havePlugIn = true
tiny.close()
}
return havePlugIn
}

var haveShockwavePlugIn = probePlugIn("application/x-director")```

close (document object), reload, replace, write, writeln methods

# open (window object)

Method. Opens a new web browser window.

### Syntax

`[windowVar = ][window].open("URL", "windowName", ["windowFeatures"])`

### Parameters

windowVar is the name of a new window. Use this variable when referring to a window's properties, methods, and containership.

URL specifies the URL to open in the new window. See the location object for a description of the URL components.

windowName is the window name to use in the TARGET attribute of a FORM or <A> tag. windowName can contain only alphanumeric or underscore (_) characters.

windowFeatures is a comma-separated list of any of the following options and values:

```   toolbar[=yes|no]|[=1|0]
location[=yes|no]|[=1|0]
directories[=yes|no]|[=1|0]
status[=yes|no]|[=1|0]
scrollbars[=yes|no]|[=1|0]
resizable[=yes|no]|[=1|0]
width=pixels
height=pixels```
You may use any subset of these options. Separate options with a comma. Do not put spaces between the options. The windowFeatures are:

• toolbar creates the standard Navigator toolbar, with buttons such as Back and Forward, if true.
• location creates a Location entry field, if true.
• directories creates the standard Navigator directory buttons, such as What's New and What's Cool, if true.
• status creates the status bar at the bottom of the window, if true.
• menubar creates the menu at the top of the window, if true.
• scrollbars creates horizontal and vertical scrollbars when the document grows larger than the window dimensions, if true.
• resizable allows a user to resize the window, if true.
• width specifies the width of the window in pixels.
• height specifies the height of the window in pixels.

### Method of

window object

### Implemented in

Navigator 2.0

### Description

The open method opens a new Web browser window on the client, similar to choosing New Web Browser from the File menu of the Navigator. The URL argument specifies the URL contained by the new window. If URL is an empty string, a new, empty window is created.

In event handlers, you must specify window.open() instead of simply using open(). Due to the scoping of static objects in JavaScript, a call to open() without specifying an object name is equivalent to document.open().

windowFeatures is an optional, comma-separated list of options for the new window. The Boolean windowFeatures options are set to true if they are specified without values, or as yes or 1. For example, open("", "messageWindow", "toolbar") and open("", "messageWindow", "toolbar=1") both set the toolbar option to true. If windowName does not specify an existing window and you do not specify windowFeatures, all Boolean windowFeatures are true by default. If you specify any item in windowFeatures, all other Boolean windowFeatures are false unless you explicitly specify them. After a window is open, you cannot use JavaScript to change the windowFeatures.

You can use open on an existing window, and if you pass the empty string for the URL, you will get a reference to the existing window, but not load anything into it. You can, for example, then look for properties in the window.

### Examples

In the following example, the windowOpener function opens a window and uses write methods to display a message:

```function windowOpener() {
msgWindow.document.write
msgWindow.document.write
("<CENTER><BIG><B>Hello, world!</B></BIG></CENTER>")
}```
The following is an onClick event handler that opens a new client window displaying the content specified in the file sesame.html. The window opens with the specified option settings; all other options are false because they are not specified.

```<FORM NAME="myform">
<INPUT TYPE="button" NAME="Button1" VALUE="Open Sesame!"
onClick="window.open ('sesame.html', 'newWin',
'scrollbars=yes,status=yes,width=300,height=300')">
</FORM>```
Notice the use of single quotes (') inside the onClick event handler.

close (window object) method

# opener

Property. Specifies the window of the calling document when a window is opened using the open method.

### Syntax

`window.opener`

### Property of

window object

### Implemented in

Navigator 3.0

No

### Description

When a source document opens a destination window by calling the open method, the opener property specifies the window of the source document. Evaluate the opener property from the destination window.

This property persists across document unload in the opened window.

You can change the opener property at any time.

### Examples

Example 1: Close the opener. The following code closes the window that opened the current window. When the opener window closes, opener is unchanged. However, window.opener.name then evaluates to undefined.

`window.opener.close()`
Example 2: Evaluate the name of the opener. A window can determine the name of its opener as follows:

`document.write("<BR>opener property is " + window.opener.name)`
Example 3: Change the value of opener. The following code changes the value of the opener property to null. After this code executes, you cannot close the opener window as shown in Example 1.

`window.opener=null`
Example 4: Change a property of the opener. The following code changes the background color of the window specified by the opener property.

`window.opener.document.bgColor='bisque'`

close (window object), open (window object) methods

# Option

Object. A Select object option created using the Option() constructor. For information, see the Select object.

# options

Property. An array corresponding to options in a Select object (OPTION tags) in source order. See the Select object.

# parent

Property. The parent property is a synonym for a window or frame whose frameset contains the current frame.

### Syntax

```1. parent.propertyName
2. parent.methodName
3. parent.frameName
4. parent.frames[index]```

### Parameters

propertyName is the defaultStatus, status, length, name, or parent property when the calling parent refers to a window object.

propertyName is the length, name, or parent property when the calling parent refers to a Frame object.

methodName is any method associated with the window object.

frameName and frames[index] are ways to refer to frames.

### Property of

Frame object, window object

### Implemented in

Navigator 2.0

No

### Description

The parent property refers to the FRAMESET window of a frame. Child frames within a frameset refer to sibling frames by using "parent" in place of the window name as follows: parent.frameName or parent.frames[index]. For example, if the fourth frame in a set has NAME="homeFrame," sibling frames can refer to that frame using parent.homeFrame or parent.frames[3].

You can use parent.parent to refer to the "grandparent" frame or window when a <FRAMESET> tag is nested within a child frame.

The parent property is read-only. The value of the parent property is

`     <object nameAttribute>`
where nameAttribute is the NAME attribute if the parent is a frame, or an internal reference if the parent is a window.

### Examples

See the examples for the Frame object.

# parse

Method. Returns the number of milliseconds in a date string since January 1, 1970, 00:00:00, local time.

### Syntax

`Date.parse(dateString)`

### Parameters

dateString is a string representing a date or a property of an existing object.

Date

### Implemented in

Navigator 2.0

### Description

The parse method takes a date string (such as "Dec 25, 1995") and returns the number of milliseconds since January 1, 1970, 00:00:00 (local time). This function is useful for setting date values based on string values, for example in conjunction with the setTime method and the Date object.

Given a string representing a time, parse returns the time value. It accepts the IETF standard date syntax: "Mon, 25 Dec 1995 13:30:00 GMT." It understands the continental US time-zone abbreviations, but for general use, use a time-zone offset, for example, "Mon, 25 Dec 1995 13:30:00 GMT+0430" (4 hours, 30 minutes west of the Greenwich meridian). If you do not specify a time zone, the local time zone is assumed. GMT and UTC are considered equivalent.

Because the parse function is a static method of Date, you always use it as Date.parse(), rather than as a method of a Date object you created.

### Examples

If IPOdate is an existing Date object, then

`IPOdate.setTime(Date.parse("Aug 9, 1995"))`

UTC method

# parseFloat

Function. Parses a string argument and returns a floating point number.

### Syntax

`parseFloat(string)`

### Parameters

string is a string that represents the value you want to parse.

### Implemented in

• Navigator 2.0
• Navigator 3.0: returns "NaN" on all platforms if the first character of the string specified in parseFloat(string) cannot be converted to a number. In previous releases, it returned "NaN" on Solaris and Irix and zero on all other platforms.

### Description

The parseFloat function is a built-in JavaScript function. It is not a method associated with any object, but is part of the language itself.

parseFloat parses its argument, a string, and returns a floating point number. If it encounters a character other than a sign ( + or -), numeral (0-9), a decimal point, or an exponent, then it returns the value up to that point and ignores that character and all succeeding characters.

If the first character cannot be converted to a number, parseFloat returns "NaN".

For arithmetic purposes, the "NaN" value is not a number in any radix. You can call the isNaN function to determine if the result of parseFloat is "NaN." If "NaN" is passed on to arithmetic operations, the operation results will also be "NaN."

### Examples

The following examples all return 3.14:

```parseFloat("3.14")
parseFloat("314e-2")
parseFloat("0.0314E+2")
var x = "3.14"
parseFloat(x)```
The following example returns "NaN":

`parseFloat("FF2")`

isNaN, parseInt functions

# parseInt

Function. Parses a string argument and returns an integer of the specified radix or base.

### Syntax

`parseInt(string [,radix])`

### Parameters

string is a string that represents the value you want to parse.

radix is an integer that represents the radix of the return value.

### Implemented in

• Navigator 2.0
• Navigator 3.0: returns "NaN" on all platforms if the first character of the string specified in parseInt(string) cannot be converted to a number. In previous releases, it returned "NaN" on Solaris and Irix and zero on all other platforms.

### Description

The parseInt function is a built-in JavaScript function. It is not a method associated with any object, but is part of the language itself.

The parseInt function parses its first argument, a string, and attempts to return an integer of the specified radix (base). For example, a radix of 10 indicates to convert to a decimal number, 8 octal, 16 hexadecimal, and so on. For radixes above 10, the letters of the alphabet indicate numerals greater than 9. For example, for hexadecimal numbers (base 16), A through F are used.

If parseInt encounters a character that is not a numeral in the specified radix, it ignores it and all succeeding characters and returns the integer value parsed up to that point. parseInt truncates numbers to integer values.

If the radix is not specified or is specified as zero, JavaScript assumes the following:

• If the input string begins with "0x," the radix is 16 (hexadecimal).
• If the input string begins with "0," the radix is eight (octal).
• If the input string begins with any other value, the radix is 10 (decimal).
If the first character cannot be converted to a number, parseInt returns "NaN".

For arithmetic purposes, the "NaN" value is not a number in any radix. You can call the isNaN function to determine if the result of parseInt is "NaN." If "NaN" is passed on to arithmetic operations, the operation results will also be "NaN."

### Examples

The following examples all return 15:

```parseInt("F", 16)
parseInt("17", 8)
parseInt("15", 10)
parseInt(15.99, 10)
parseInt("FXX123", 16)
parseInt("1111", 2)
parseInt("15*3", 10)```
The following examples all return "NaN":

```parseInt("Hello", 8)
parseInt("0x7", 10)
parseInt("FFF", 10)```
Even though the radix is specified differently, the following examples all return 17 because the input string begins with "0x."

```parseInt("0x11", 16)
parseInt("0x11", 0)
parseInt("0x11")```

isNaN, parseFloat functions; valueOf method

Object. A text field on an HTML form that conceals its value by displaying asterisks (*). When the user enters text into the field, asterisks (*) hide entries from view.

### HTML syntax

To define a Password object, use standard HTML syntax:

```<INPUT
[VALUE="textValue"]
SIZE=integer
[onBlur="handlerText"]
[onFocus="handlerText"]>```

### HTML attributes

NAME="passwordName" specifies the name of the Password object. You can access this value using the name property, and you can use this name when indexing the elements array.

VALUE="textValue" specifies the initial value of the Password object. You can access this value using the defaultValue property.

SIZE=integer specifies the number of characters the Password object can accommodate without scrolling.

### Syntax

To use a Password object's properties and methods:

```1. passwordName.propertyName
3. formName.elements[index].propertyName
4. formName.elements[index].methodName(parameters)```

### Parameters

passwordName is the value of the NAME attribute of a Password object.

formName is either the value of the NAME attribute of a Form object or an element in the forms array.

index is an integer representing a Password object on a form or the name of a Password object as specified by the NAME attribute.

propertyName is one of the properties listed below.

methodName is one of the methods listed below.

Form object

### Implemented in

• Navigator 2.0
• Navigator 3.0: added type property; added onBlur and onFocus event handlers

### Description

A Password object on a form looks as follows:

A Password object is a form element and must be defined within a <FORM> tag.

If a user interactively modifies the value in a password field, you cannot evaluate it accurately unless data tainting is enabled. See "Using data tainting for security" and the value property.

### Properties

The Password object has the following properties:

Property Description
defaultValue Reflects the VALUE attribute
form property Specifies the form containing the Password object
name Reflects the NAME attribute
type Reflects the TYPE attribute
value Reflects the current value of the Password object's field

### Methods

The Password object has the following methods:
 blur eval focus select method toString valueOf

### Examples

The following example creates a Password object with no default value:

`<B>Password:</B> <INPUT TYPE="password" NAME="password" VALUE="" SIZE=25>`

Form object, Text object

# pathname

Property. A string specifying the url-path portion of the URL.

### Syntax

```1. links[index].pathname
2. location.pathname
3. areaName.pathname```

### Parameters

index is an integer representing a Link object or the name of a Link object as specified by the NAME attribute.

areaName is the value of the NAME attribute of an Area object.

### Property of

Area object (see Link object), Link object, location object

### Implemented in

• Navigator 2.0
• Navigator 3.0: property of Area

Yes

### Description

The pathname property specifies a portion of the URL. The pathname supplies the details of how the specified resource can be accessed.

You can set the pathname property at any time, although it is safer to set the href property to change a location. If the pathname that you specify cannot be found in the current location, you will get an error.

In event handlers, you must specify window.location.pathname instead of simply using location.pathname. Due to the scoping of static objects in JavaScript, a call to location without specifying an object name is equivalent to document.location, which is a synonym for document.URL.

See Section 3.1 of RFC 1738 for complete information about the pathname.

### Examples

See the examples for the href property.

hash, host, hostname, href, port, protocol, search properties

# PI

Property. The ratio of the circumference of a circle to its diameter, approximately 3.14159.

### Syntax

`Math.PI`

Math

### Implemented in

Navigator 2.0

No

### Description

Because PI is a constant, it is a read-only property of Math.

### Examples

The following function returns the value of pi:

```function getPi() {
return Math.PI
}```

E, LN2, LN10, LOG2E, LOG10E, SQRT1_2, SQRT2 properties

# Plugin

Object. A plug-in module installed on the client.

### Syntax

To use a Plugin object:

```1. navigator.plugins[index].propertyName
2. navigator.plugins[pluginIndex][mimeTypeIndex].mimeTypePropertyName```

### Parameters

index is an integer representing a plug-in installed on the client or a string containing the type of a Plugin object (from the type property).

mimeTypeIndex is either an integer representing a MIME type supported by the plug-in or a string containing the type of a MimeType object (from the type property).

propertyName is one of the properties listed below.

mimeTypePropertyName is a property of a MimeType object. See MimeType for a list of properties.

### Property of

The plugins array is a property of navigator.

The Plugin object is a member of the plugins array.

### Implemented in

Navigator 3.0

### Description

A Plugin object is a plug-in installed on the client. A plug-in is a software module that Navigator can invoke to display specialized types of embedded data within the browser. The user can obtain a list of installed plug-ins by choosing About Plug-ins from the Help menu.

Each Plugin object is an array containing one element for each MIME type supported by the plug-in. Each element of the array is a MimeType object. You can access the MimeType objects using form 2 of the syntax. For example, the following code displays the type and description properties of the first Plugin object's first MimeType object.

```myPlugin=navigator.plugins[0]
myMimeType=myPlugin[0]
document.writeln('myMimeType.type is ',myMimeType.type,"<BR>")
document.writeln('myMimeType.description is ',myMimeType.description)```
The preceding code displays output similar to the following:

```myMimeType.type is video/quicktime
myMimeType.description is QuickTime for Windows```
The Plugin object lets you dynamically determine which plug-ins are installed on the client. You can write scripts to display embedded plug-in data if the appropriate plug-in is installed, or display some alternative information such as images or text if not.

Plug-ins can be platform dependent and configurable, so a Plugin object's array of MimeType objects can vary from platform to platform, and from user to user.

Each Plugin object is an element in the plugins array.

When you use the <EMBED> tag to generate output from a plug-in application, you are not creating a Plugin object. Use the embeds array to reference plug-in instances created with <EMBED> tags. See the embeds array.

#### The plugins array

You can reference the Plugin objects installed on the client by using the plugins array. This array contains an entry for each plug-in installed on the client in source order. Each element of the plugins array is a Plugin object. For example, if three plug-ins are installed on the client, these plug-ins are reflected as navigator.plugins[0], navigator.plugins[1], and navigator.plugins[2].

To use the plugins array:

```1. navigator.plugins[index]
2. navigator.plugins.length```
index is an integer representing a plug-in installed on the client or a string containing the name of a Plugin object (from the name property).

To obtain the number of plug-ins installed on the client, use the length property: navigator.plugins.length.

Elements in the plugins array are read-only. For example, the statement navigator.plugins[0]="LiveAudio" has no effect.

### Properties

The Plugin object has the following properties:

Property Description
description A description supplied by the plug-in itself
filename The name of the plug-in file on disk
length The number of elements in the plug-in's array of MimeType objects
name The name of the plug-in

The plugins array has the following properties:

Property Description
length Reflects the number of plug-ins installed on the client

### Methods

The Plugin object has the following methods:

The plugins array has the following methods:

None.

### Examples

Example 1. The user can obtain a list of installed plug-ins by choosing About Plug-ins from the Help menu. To see the code Navigator uses for this report, choose About Plug-ins from the Help menu, then choose Document Source from the View menu.

Example 2. The following code assigns shorthand variables for the predefined LiveAudio properties.

```var myPluginName = navigator.plugins["LiveAudio"].name
var myPluginFile = navigator.plugins["LiveAudio"].filename
var myPluginDesc = navigator.plugins["LiveAudio"].description```
Example 3. The following code displays the message "LiveAudio is configured for audio/wav" if the LiveAudio plug-in is installed and is enabled for the "audio/wav" MIME type:

```var myPlugin = navigator.plugins["LiveAudio"]
var myType = myPlugin["audio/wav"]
if (myType && myType.enabledPlugin == myPlugin)
document.writeln("LiveAudio is configured for audio/wav")```
Example 4. The following expression represents the number of MIME types that Shockwave can display:

`navigator.plugins["Shockwave"].length`
Example 5. The following code displays the name, filename, description, and length properties for each Plugin object on a client:

```document.writeln("<TABLE BORDER=1><TR VALIGN=TOP>",
"<TH ALIGN=left>i",
"<TH ALIGN=left>name",
"<TH ALIGN=left>filename",
"<TH ALIGN=left>description",
"<TH ALIGN=left># of types</TR>")
for (i=0; i < navigator.plugins.length; i++) {
document.writeln("<TR VALIGN=TOP><TD>",i,
"<TD>",navigator.plugins[i].name,
"<TD>",navigator.plugins[i].filename,
"<TD>",navigator.plugins[i].description,
"<TD>",navigator.plugins[i].length,
"</TR>")
}
document.writeln("</TABLE>")```
The preceding example displays output similar to the following:
 i name filename description # of types 0 QuickTime Plug-In d:\nettools\netscape\nav30\Program\ plugins\NPQTW32.DLL QuickTime Plug-In for Win32 v.1.0.0 1 1 LiveAudio d:\nettools\netscape\nav30\Program\ plugins\NPAUDIO.DLL LiveAudio - Netscape Navigator sound playing component 7 2 NPAVI32 Dynamic Link Library d:\nettools\netscape\nav30\Program\ plugins\npavi32.dll NPAVI32, avi plugin DLL 2 3 Netscape Default Plugin d:\nettools\netscape\nav30\Program\ plugins\npnul32.dll Null Plugin 1

MimeType object; embeds array

# plugins

Property. An array of all plug-ins currently installed on the client. See the Plugin object for information.

No

# port

Property. A string specifying the communications port that the server uses for communications.

### Syntax

```1. links[index].port
2. location.port
3 areaName.port```

### Parameters

index is an integer representing a Link object or the name of a Link object as specified by the NAME attribute.

areaName is the value of the NAME attribute of an Area object.

### Property of

Area object (see Link object), Link object, location object

### Implemented in

• Navigator 2.0
• Navigator 3.0: property of Area

Yes

### Description

The port property specifies a portion of the URL. The port property is a substring of the hostname property. The hostname property is the concatenation of the host and port properties, separated by a colon. When the port property is 80 (the default), the host property is the same as the hostname property.

You can set the port property at any time, although it is safer to set the href property to change a location. If the port that you specify cannot be found in the current location, you will get an error. If the port property is not specified, it defaults to 80 on the server.

In event handlers, you must specify window.location.port instead of simply using location.port. Due to the scoping of static objects in JavaScript, a call to location without specifying an object name is equivalent to document.location, which is a synonym for document.URL.

See Section 3.1 of RFC 1738 for complete information about the port.

### Examples

See the examples for the href property.

hash, host, hostname, href, pathname, protocol, search properties

# POSITIVE_INFINITY

Property. A special numeric value representing infinity. This value is represented as "Infinity".

### Syntax

`Number.POSITIVE_INFINITY`

Number

### Implemented in

Navigator 3.0

No

### Description

This value behaves mathematically like an infinity; for example, anything multiplied by infinity is infinity, and anything divided by infinity is zero.

JavaScript does not have a literal for Infinity.

Because POSITIVE_INFINITY is a constant, it is a read-only property of Number.

### Examples

In the following example, the variable bigNumber is assigned a value that is larger than the maximum value. When the if statement executes, bigNumber has the value "Infinity", so the func1 function is called.

```var bigNumber = Number.MAX_VALUE * 10
if (bigNumber == Number.POSITIVE_INFINITY)
func1()
else
func2()```

MAX_VALUE, MIN_VALUE, NaN, NEGATIVE_INFINITY properties

# pow

Method. Returns base to the exponent power, that is, baseexponent.

### Syntax

`Math.pow(base, exponent)`

### Parameters

base is any numeric expression or a property of an existing object.

exponent is any numeric expression or a property of an existing object.

Math

### Implemented in

Navigator 2.0

### Examples

```function raisePower(x,y) {
return Math.pow(x,y)
}```
If x equals seven and y equals two, raisePower returns 49 (seven to the power of two).

exp, log methods

# previous

Property. A string specifying the complete URL of the previous history entry.

### Syntax

`history.previous`

### Property of

history object

### Implemented in

Navigator 3.0

Yes

### Description

The previous property reflects the URL that would be used if the user chose Back from the Go menu. This property has a value only if data tainting is enabled; if data tainting is not enabled, previous has no value.

previous is a read-only property.

### Examples

The following example determines whether history.previous contains the string "NETSCAPE.COM". If it does, the function myFunction is called.

```if (history.previous.indexOf("NETSCAPE.COM") != -1) {
myFunction(history.previous)
}```

current, next properties; "Using data tainting for security"

# prompt

Method. Displays a Prompt dialog box with a message and an input field.

### Syntax

`prompt(message, [inputDefault])`

### Parameters

message is any string or a property of an existing object; the string is displayed as the message.

inputDefault is a string, integer, or property of an existing object that represents the default value of the input field.

### Method of

window object

### Implemented in

Navigator 2.0

### Description

A prompt dialog box looks as follows:

Use the prompt method to display a dialog box that receives user input. If you do not specify an initial value for inputDefault, the dialog box displays "<undefined>."

Although prompt is a method of the window object, you do not need to specify a windowReference when you call it. For example, windowReference.prompt() is unnecessary.

You cannot specify a title for a prompt dialog box, but you can use the open method to create your own "prompt" dialog. See open (window object).

### Examples

`prompt("Enter the number of cookies you want to order:", 12)`

# protocol

Property. A string specifying the beginning of the URL, up to and including the first colon.

### Syntax

```1. links[index].protocol
2. location.protocol
3 areaName.protocol```

### Parameters

index is an integer representing a Link object or the name of a Link object as specified by the NAME attribute.

areaName is the value of the NAME attribute of an Area object.

### Property of

Area object (see Link object), Link object, location object

### Implemented in

• Navigator 2.0
• Navigator 3.0: property of Area

Yes

### Description

The protocol property specifies a portion of the URL. The protocol indicates the access method of the URL. For example, a protocol of "http:" specifies HyperText Transfer Protocol, and a protocol of "javascript:" specifies JavaScript code.

You can set the protocol property at any time, although it is safer to set the href property to change a location. If the protocol that you specify cannot be found in the current location, you will get an error.

In event handlers, you must specify window.location.protocol instead of simply using location.protocol. Due to the scoping of static objects in JavaScript, a call to location without specifying an object name is equivalent to document.location, which is a synonym for document.URL.

The protocol property represents the scheme name of the URL. See Section 2.1 of RFC 1738 for complete information about the protocol.

### Examples

See the examples for the href property.

hash, host, hostname, href, pathname, port, search properties

# prototype

Property. Defines a property that is shared by all objects of the specified type.

### Syntax

`objectType.prototype.propertyName = value`

### Parameters

objectType is the name of a constructor or function specifying an object type.

propertyName is the name of the property to be created.

value is the property value initially assigned for all objects of the specified objectType.

### Property of

prototype is a property of any object created with new, such as the following:
 Array Boolean Date Function Image Number Select object option String User-defined objects (see "Creating new objects")

### Implemented in

Navigator 3.0

No

### Description

Use the prototype property to explicitly add properties to objects created with the new operator.

For example, you can create Date objects by using the Date() constructor and the new operator. Date.prototype refers to the prototype object for the Date() constructor. If you set a property for the prototype, such as Date.prototype.description, then all objects created with Date() will have the description property, even if the objects already exist.

```var today = new Date()
var birthday = new Date(95,12,17)
Date.prototype.description=null
today.description="Oh what a beautiful mornin\'"
birthday.description="The day you were born"```
After you set a property for the prototype, all subsequent objects created with Date() will have the property:

```startDate=new Date()
startDate.description="Started the daily grind"```

### Examples

Example 1: Add a property to a user-defined object. The following example uses the function Car to define a Car object type. It then uses new to create myCar, an instance of the object. The code Car.prototype.wheels=4 adds the wheels property to all instances of the Car object.

```function Car(make, model, year) {
this.make = make
this.model = model
this.year = year
}

var myCar = new Car("Acura", "Integra", 1987)
Car.prototype.wheels = 4        // no 3-wheelers please!

if (myCar.wheels == 4)
document.write("The car myCar has ", myCar.wheels, " wheels.")```
Example 2: Add a method to String objects. The following example creates a method, str_rep, and uses the statement String.prototype.rep = str_rep to add the method to all String objects. All objects created with new String() then have that method, even objects already created. The example then creates an alternate method and adds that to one of the String objects using the statement s1.rep = fake_rep. The str_rep method of the remaining String objects is not altered.

```var s1 = new String("a")
var s2 = new String("b")
var s3 = new String("c")

// Create a repeat-string-N-times method for all String objects
function str_rep(n) {
var s = "", t = this.toString()
while (--n >= 0) s += t
return s
}
String.prototype.rep = str_rep

// Display the results
document.write("<P>s1.rep(3) is " + s1.rep(3))     // "aaa"
document.write("<BR>s2.rep(5) is " + s2.rep(5))    // "bbbbb"
document.write("<BR>s3.rep(2) is " + s3.rep(2))    // "cc"

// Create an alternate method and assign it to only one String variable
function fake_rep(n) {
return "repeat " + this + n + " times."
}

s1.rep = fake_rep

document.write("<P>s1.rep(1) is " + s1.rep(1))    // "repeat a 1 times."
document.write("<BR>s2.rep(4) is " + s2.rep(4))   // "bbbb"
document.write("<BR>s3.rep(6) is " + s3.rep(6))            // "cccccc"```
This example produces the following output:

```s1.rep(3) is aaa
s2.rep(5) is bbbbb
s3.rep(2) is cc```
```s1.rep(1) is repeat a1 times.
s2.rep(4) is bbbb
s3.rep(6) is cccccc```
The function in this example also works on String objects not created with the String() constructor. The following code returns "zzz".

`"z".rep(3)`