Contains an array of information on the URLs that the client has visited within a window. This information is stored in a history list and is accessible through the browser's Go menu.

Client-side object
Implemented in	Navigator 2.0 Navigator 3.0: added `current, next,` and `previous` properties;

Created by

History objects are predefined JavaScript objects that you access through the history property of a Window object.

Description

To change a window's current URL without generating a history entry, you can use the Location.replace method. This replaces the current page with a new one without generating a history entry. See Location.replace.

You can refer to the history entries by using the Window.history array. This array contains an entry for each history entry in source order. Each array entry is a string containing a URL. For example, if the history list contains three named entries, these entries are reflected as history[0], history[1], and history[2].

If you access the history array without specifying an array element, the browser returns a string of HTML which displays a table of URLs, each of which is a link.

Property Summary

`current`	Specifies the URL of the current history entry.
`length`	Reflects the number of entries in the history list.
`next`	Specifies the URL of the next history entry.
`previous`	Specifies the URL of the previous history entry.

Method Summary

`back`	Loads the previous URL in the history list.
`forward`	Loads the next URL in the history list.
`go`	Loads a URL from the history list.

Examples

Example 1. The following example goes to the URL the user visited three clicks ago in the current window.

history.go(-3)

Example 2. You can use the history object with a specific window or frame. The following example causes window2 to go back one item in its window (or session) history:

window2.history.back()

Example 3. The following example causes the second frame in a frameset to go back one item:

parent.frames[1].history.back()

Example 4. The following example causes the frame named frame1 in a frameset to go back one item:

parent.frame1.history.back()

Example 5. The following example causes the frame named frame2 in window2 to go back one item:

window2.frame2.history.back()

Example 6. The following code determines whether the first entry in the history array contains the string "NETSCAPE". If it does, the function myFunction is called.

if (history[0].indexOf("NETSCAPE") != -1) {
   myFunction(history[0])
}

Example 7. The following example displays the entire history list:

document.writeln("<B>history is</B> " + history)

This code displays output similar to the following:

history is
Welcome to Netscape http://home.netscape.com/
Sun Microsystems http://www.sun.com/
Royal Airways http://www.supernet.net/~dugbrown/

Properties

current

A string specifying the complete URL of the current history entry.

Property of	`History`
Read-only
Implemented in	Navigator 3.0

Security

Navigator 3.0: This property is tainted by default. It has no value of data tainting is disabled. For information on data tainting, see "JavaScript Security".

Navigator 4.0: Getting the value of this property requires the UniversalBrowserRead privilege. It has no value if you do not have this privilege. For information on security in Navigator 4.0, see Chapter 7, "JavaScript Security," in the JavaScript Guide.

Examples

The following example determines whether history.current contains the string "netscape.com". If it does, the function myFunction is called.

if (history.current.indexOf("netscape.com") != -1) {
   myFunction(history.current)
}

length

The number of elements in the history array.

Property of	`History`
Read-only
Implemented in	Navigator 2.0

Security

Navigator 4.0: Getting the value of this property requires the UniversalBrowserRead privilege. For information on security in Navigator 4.0, see Chapter 7, "JavaScript Security," in the JavaScript Guide.

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

Property of	`History`
Read-only
Implemented in	Navigator 3.0

Security

Navigator 3.0: This property is tainted by default. It has no value of data tainting is disabled. For information on data tainting, see "JavaScript Security".

Description

The next property reflects the URL that would be used if the user chose Forward from the Go menu.

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)
}

Security

Navigator 3.0: This property is tainted by default. It has no value of data tainting is disabled. For information on data tainting, see "JavaScript Security".

Description

The previous property reflects the URL that would be used if the user chose Back from the Go menu.

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)
}

Methods

back

Loads the previous URL in the history list.

Method of	`History`
Implemented in	Navigator 2.0

Syntax

back()

Parameters

None

Description

This method performs the same action as a user choosing the Back button in the browser. The back method is the same as history.go(-1).

Examples

The following custom buttons perform the same operation as the browser's Back button:

<P><INPUT TYPE="button" VALUE="< Go Back"
   onClick="history.back()">
<P><INPUT TYPE="button" VALUE="> Go Back"
   onClick="myWindow.back()">

forward

Loads the next URL in the history list.

Method of	`History`
Implemented in	Navigator 2.0

Syntax

forward()

Parameters

None

Description

This method performs the same action as a user choosing the Forward button in the browser. The forward method is the same as history.go(1).

Examples

The following custom buttons perform the same operation as the browser's Forward button:

<P><INPUT TYPE="button" VALUE="< Forward"
   onClick="history.forward()">
<P><INPUT TYPE="button" VALUE="> Forward"
   onClick="myWindow.forward()">

go

Loads a URL from the history list.

Method of	`History`
Implemented in	Navigator 2.0

Syntax

go(delta)
go(location)

Parameters

delta	An integer representing a relative position in the history list.
location	A string representing all or part of a URL in the history list.

Description

The go method navigates to the location in the history list determined by the specified parameter.

If the delta argument is 0, the browser reloads the current page. If it is an integer greater than 0, the go method loads the URL that is that number of entries forward in the history list; otherwise, it loads the URL that is that number of entries backward in the history list.

The location argument is a string. Use location to load the nearest history entry whose URL contains location as a substring. Matching the URL to the location parameter is case-insensitive. Each section of a URL contains different information. See Location for a description of the URL components.

The go method creates a new entry in the history list. To load a URL without creating an entry in the history list, use Location.replace.

Examples

The following button navigates to the nearest history entry that contains the string "home.netscape.com":

<P><INPUT TYPE="button" VALUE="Go"
   onClick="history.go('home.netscape.com')">

The following button navigates to the URL that is three entries backward in the history list:

<P><INPUT TYPE="button" VALUE="Go"
   onClick="history.go(-3)">

screen

Contains properties describing the display screen and colors.

Client-side object
Implemented in	Navigator 4.0

Created by

The JavaScript runtime engine creates the screen object for you. You can access its properties automatically.

Description

This object contains read-only properties that allow you to get information about the user's display.

Property Summary

`availHeight`	Specifies the height of the screen, in pixels, minus permanent or semipermanent user interface features displayed by the operating system, such as the Taskbar on Windows.
`availWidth`	Specifies the width of the screen, in pixels, minus permanent or semipermanent user interface features displayed by the operating system, such as the Taskbar on Windows.
`colorDepth`	The bit depth of the color palette, if one is in use; otherwise, the value is derived from `screen.pixelDepth`.
`height`	Display screen height.
`pixelDepth`	Display screen color resolution (bits per pixel).
`width`	Display screen width.

Examples

The following function creates a string containing the current display properties:

function screen_properties() {
   document.examples.results.value = "("+screen.width+" x
      "+screen.height+") pixels, "+
      screen.pixelDepth +" bit depth, "+
      screen.colorDepth +" bit color palette depth.";
} // end function screen_properties

Properties

availHeight

Specifies the height of the screen, in pixels, minus permanent or semipermanent user interface features displayed by the operating system, such as the Taskbar on Windows.

Property of	`screen`
Implemented in	Navigator 4.0

availWidth

Specifies the width of the screen, in pixels, minus permanent or semipermanent user interface features displayed by the operating system, such as the Taskbar on Windows.

Property of	`screen`
Implemented in	Navigator 4.0

colorDepth

The bit depth of the color palette in bits per pixel, if a color palette is in use. Otherwise, this property is derived from screen.pixelDepth.

Property of	`screen`
Implemented in	Navigator 4.0

height

Display screen height, in pixels.

Property of	`screen`
Implemented in	Navigator 4.0

pixelDepth

Display screen color resolution, in bits per pixel.

Property of	`screen`
Implemented in	Navigator 4.0

width

Display screen width, in pixels.

Property of	`screen`
Implemented in	Navigator 4.0

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History

Created by

Description

Property Summary

Method Summary

Examples

See also

Properties

current

Security

Examples

See also

length

Security

next

Security

Description

Examples

See also

previous

Security

Description

Examples

See also

Methods

back

Syntax

Parameters

Description

Examples

See also

forward

Syntax

Parameters

Description

Examples

See also

go

Syntax

Parameters

Description

Examples

See also

screen

Created by

Description

Property Summary

Examples

Properties

availHeight

availWidth

colorDepth

height

pixelDepth

width