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Introduction

This document describes the changes and new features for JavaScript in Navigator 4.0. For additional information about JavaScript, see the JavaScript section of the DevEdge library.

• "Feature Summary" provides a summary of the new and changed features. * indicates a change to an existing feature.
• "Compatibility With Earlier Versions of Navigator" describes how write scripts for different versions of Navigator.

In addition to the information in this document, DevEdge contains other articles and tutorials explaining the use of some of the new features of JavaScript 1.2. For example, visit View Source, Netscape's online technical magazine for developers, or JavaScript Developer Central, a centralized location for much information about JavaScript, including sample code, tech notes, and other articles.

The event model, as described in Chapter 1, "Event Model," has changed to include a new event object, new events, and event capturing.

• "The event Object" on page 21 contains properties that describe a JavaScript event, such as the event type and the cursor location at the time of the event. The object is passed as an argument to an event handler when an event occurs.
• "Event Capturing" on page 24 enables a window or document to capture an event before the target object (link, button, etc.) gets the event. The window and document objects have these new methods to support event capturing:
• captureEvents--sets the window or document to capture the specified events.
• disableExternalCapture--disables external event capturing set by the enableExternalCapture method.
• enableExternalCapture--allows a window with frames to capture events in pages loaded from different locations (servers).
• releaseEvents--sets the window or document to release the specified events.

Objects that receive events have these new methods for event capturing:

• routeEvent--routes the event from its capturer through its normal event hierarchy.
• handleEvent--fires the event handler for the specified event.
• Events have been added or revised.
• Click*--occurs when a user clicks a link or form element.
• DblClick--occurs when a user double-clicks over a link or form element.
• DragDrop--occurs when a user drops an object onto a Navigator window.
• KeyDown--occurs when a user depresses a key.
• KeyPress--occurs when a user presses or holds down a key.
• KeyUp--occurs when a user releases a key.
• MouseDown--occurs when a user depresses a mouse button.
• MouseMove--occurs when a user moves the cursor.
• MouseOut*--occurs when a user moves the cursor out of an object.
• MouseOver*--occurs when a user moves the cursor over an object.
• MouseUp--occurs when a user releases a mouse button.
• Move--occurs when a user or script moves a window.
• Resize--occurs when a user or script resizes a window.

• You can nest functions within functions. (That is, JavaScript now supports lambda expresisons and lexical closures.)
• Number--converts a specified object to a number.
• String--converts a specified object to a string.

For information on using layers, see Dynamic HTML in Netscape Communicator. Note that this link takes you to a different set of documents.

• concat--joins two arrays and returns a new array.
• pop removes the last element from an array and returns that element.
• push adds one or more elements to the end of an array and returns that last element added.
• shift removes the first element from an array and returns that element
• unshift adds one or more elements to the front of an array and returns the new length of the array.
• slice--extracts a section from an array and returns a new array
• splice--adds and/or removes elements from an array and returns the removed elements.
• sort*--now works on all platforms. It no longer converts undefined elements to null; instead, it sorts them to the high end of the array.

• getSelection--returns a string containing the text of the current selection.

• preference--allows a script to get and set certain Navigator preferences, such as enabling or disabling Java.

• charCodeAt--returns a number specifying the ISO-Latin-1 codeset value of the character at the specified index in a string object.
• concat--combines the text of two strings and returns a new string.
• fromCharCode--constructs a string from a specified sequence of numbers that are ISO-Latin-1 codeset values.
• match--executes a search for a match between a string and a regular expression.
• replace--executes a search for a match between a string and a regular expression, and replaces the matched substring with a new substring.
• search--tests for a match between a string and a regular expression
• slice--extracts a section of an string and returns a new string.
• split*--includes the following new features and changes:
• It can take a regular expression argument, as well as a fixed string, by which to split the object string.
• It can take a limit count so that it won't include trailing empty elements in the resulting array.
• If you specify LANGUAGE="JavaScript1.2" in the <SCRIPT> tag, string.split(" ") splits on any run of one or more white space characters including spaces, tabs, line feeds, and carriage returns.
• substr--returns the characters in a string collecting the specified number of characters beginning with a specified location in the string.
• substring*--if you specify LANGUAGE="JavaScript1.2" in the <SCRIPT> tag, this method no longer swaps index numbers when the first index is greater than the second.

• back--undoes the last history step in any frame within the top-level window, not just backing up a step in the frame in which the call to back occurs.
• clearInterval--cancels setInterval.
• disableExternalCapture--disables external capturing of events.
• enableExternalCapture--allows a window with frames to capture events in pages loaded from different locations.
• find--finds the specified text string in the contents of the window.
• forward--points the Navigator window to the next URL in the current history list.
• home--points the Navigator window to the URL specified in the preferences as the user's home page.
• moveBy--moves the window by the specified amount
• moveTo--moves the window to the specified coordinates
• open--includes the following new window features:
• alwaysLowered--forms a new window which floats below the other screen windows, whether it is currently active or not.
• alwaysRaised--forms a new window which floats on top of the other screen windows, whether it is currently active or not.
• dependent--creates a new window as a child of an existing window.
• hotkeys--enables or disables most hotkeys in a new window.
• innerHeight and innerWidth--reflect the size of the Navigator window's content area. These replace height and width, which are kept for backwards compatibility.
• outerHeight and outerWidth--reflect the size of the Navigator window's outside boundary.
• screenX--the distance the new window is placed from the left side of the screen
• screenY--the distance the new window is placed from the top of the screen
• titlebar--creates a window with a titlebar.
• z-lock--forms a new window which does not rise above other windows when given focus.
• print--prints the contents of the window.
• resizeBy--resizes the window by the specified amount
• resizeTo--resizes the window to the specified size
• scrollBy--scrolls the window by the specified amount
• scrollTo--scrolls the window to the specified coordinates
• scrollTo replaces scroll. scroll remains for backward compatibility
• setInterval--repeatedly calls a function or evaluates an expression after a specified number of milliseconds has elapsed.
• setTimeout*--can now be used to either evaluate an expression or call a function.
• stop--stops the current download.

• eval--no longer a method of individual objects; only available as a global function.
• watch--new method of all objects. Watches for a property to be assigned a value and runs a function when that occurs.
• unwatch--new method of all objects. Removes a watchpoint set with the watch method.
• captureEvents--window and document method. Sets the window or document to capture the specified events.
• handleEvent--method of all objects with event handlers. Invokes the handler for the specified event.
• releaseEvents--window and document. Sets the window or document to release the specified events.
• routeEvent--window and document method. Passes a captured event along the normal event hierarchy.
• toString*--converts the object or array to a literal. For this behavior, LANGUAGE="JavaScript1.2" must be specified in the <SCRIPT> tag.

• You can create objects using literal notation.
• arguments--includes new properties that provide information about the invoked function.
• Array*--includes the following new features and changes:
• Literal notation--arrays can now be created using literal notation
• Under JavaScript 1.2--when the <SCRIPT> tag includes LANGUAGE="JavaScript1.2", array(1) creates a new array with a[0]=1
• With regular expressions--When created as the result of a match between a regular expression and a string, arrays have new properties that provide information about the match
• Number*--now produces NaN rather than an error if x is a string that does not contain a well-formed numeric literal.
• screen--contains information about the display screen resolution and colors.
• String*--has new methods as described in "String Methods" on page 12.

• Equality operators* (== and !=)

If the <SCRIPT> tag uses LANGUAGE=JavaScript1.2, the equality operators == and != don't try to convert operands from one type to another, and always compare identity of like-typed operands.

• delete--deletes an object property or an element at a specified index in an array.

• text--contains the content of the corresponding <A> tag.

• arity--indicates the number of arguments expected by a function.

• language--indicates what translation of the Navigator is being used. This property is particularly useful for JAR management.
• platform--indicates the machine type for which the Navigator was compiled. This property is particularly useful for JAR management.

• innerHeight--specifies the vertical dimension, in pixels, of the window's content area; replaces height.
• innerWidth--specifies the horizontal dimension, in pixels, of the window's content area; replaces width.
• height--replaced by innerHeight; height remains only for backward compatibility. In earlier releases, if you set this property to a number smaller than 100, JavaScript rounded it up to 100. In 4.0, it does a security check to see if the script can set the property to a number smaller than 100.
• width--replaced by innerWidth; width remains only for backward compatibility. In earlier releases, if you set this property to a number smaller than 100, JavaScript rounded it up to 100. In 4.0, it does a security check to see if the script can set the property to a number smaller than 100.
• locationbar--object that allows you to show or hide the location bar of the targeted window.
• menubar--object that allows you to show or hide the menu bar of the targeted window.
• outerHeight--specifies the vertical dimension, in pixels, of the window's outside boundary.
• outerWidth--specifies the horizontal dimension, in pixels, of the window's outside boundary.
• pageXOffset--specifies the x-position, in pixels, of the window's viewed page.
• pageYOffset--specifies the y-position, in pixels, of the window's viewed page.
• personalbar--object that allows you to show or hide the personal bar (also known as the directories bar) of the targeted window.
• scrollbars--object that allows you to show or hide the scroll bars of the targeted window.
• statusbar--object that allows you to show or hide the status bar of the targeted window.
• toolbar--object that allows you to show or hide the tool bar of the targeted window.

Regular Expressions are patterns used to match character combinations in strings. In JavaScript, you create a regular expression as an object which has methods used to execute a match against a string. You can also pass the regular expression as arguments to the String methods match, replace, search, and split. The RegExp construction object has properties most of which are set when a match is successful, such as lastMatch which specifies the last successful match. Finally, the Array object has new properties that provide information about a successful match such as input which specifies the original input string against which the match was executed.

This section includes:

• A Description of Regular Expressions
• The Regular Expression Objects
• The RegExp Object
• String Methods
• Array Properties

• The break* and continue* statements can now be used with the new labeled statement.
• do while--repeats a loop until the test condition evaluates to false.
• export--allows a signed script to provide functions to other signed or unsigned scripts.
• import--allows a script to import functions from a signed script which has exported the information.
• labeled--allows the program to break outside nested loops or to continue a loop outside the current loop.
• switch--allows the program to test several conditions easily.

For information on using style sheets, see Dynamic HTML in Netscape Communicator. Note that this link takes you to a different set of documents.

• You can add a button to the Personal Toolbar that, when clicked, activates a JavaScript command. toolbar. See "Miscellaneous Features".

Statements within a <SCRIPT> tag are ignored if the browser does not have the level of JavaScript support specified in the LANGUAGE attribute; for example:

• Navigator 2.0 executes code within the <SCRIPT LANGUAGE="JavaScript"> tag; it ignores code within the <SCRIPT LANGUAGE="JavaScript1.1"> and <SCRIPT LANGUAGE="JavaScript1.2"> tags.
• Navigator 3.0 executes code within the <SCRIPT LANGUAGE="JavaScript"> and <SCRIPT LANGUAGE="JavaScript1.1"> tags; it ignores code within the <SCRIPT LANGUAGE="JavaScript1.2"> tag.
• Navigator 4.0 executes code within the <SCRIPT LANGUAGE="JavaScript">, <SCRIPT LANGUAGE="JavaScript1.1">, and <SCRIPT LANGUAGE="JavaScript1.2"> tags.

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Last Updated: 10/22/97 11:47:58