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Introduction

This document describes the changes and new features for JavaScript in Navigator 4.0. These features will be included in the new JavaScript Guide at a later date. For additional information about JavaScript, see the "JavaScript Guide."

• 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.

Feature Summary

Event Model

The event model has changed to include a new event object, new events, and event capturing.

• event object -- 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 -- enables a window, frame, or document to capture an event before the target object (link, button, etc.) gets the event. JavaScript implements event capturing with the following new methods:
• 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.
• 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 or frame.
• Resize -- occurs when a user or script resizes a window or frame.

Functions

• You can nest functions within functions.
• Functions can now be created with a function constructor
• Number -- converts a specified object to a number.
• String -- converts a specified object to a string.

Layers

Layers, new in Navigator 4.0, let you define overlapping layers of transparent or solid content in a web page. Each layer in HTML has a corresponding layer object that allows you to use JavaScript to manipulate the layer.

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

Methods

Array Methods

• concat -- joins two arrays and returns a new array.
• slice -- extracts a section from an array and returns a new array
• sort* -- now works on all platforms. It no longer converts undefined elements to null and sorts them to the high end of the array.

Document Method

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

Navigator Method

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

String Methods

• 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* -- no longer swaps index numbers when the first index is greater than the second. For this behavior, LANGUAGE="JavaScript1.2" must be specified in the <SCRIPT> tag.

Window Methods

• back -- points the Navigator window to the previous URL in the current history list.
• 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 -- disables most hotkeys in a new window.
• innerHeight and innerWidth -- reflect the size of the Navigator window's content area.
• replace height and width. Both 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.
• 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 extends the capabilities of scroll. scroll remains for backward compatibility
• stop -- stops the current download.

Shared Methods

• captureEvents -- window and document method. Sets the window or document to capture the specified events.
• clearInterval -- window and frame method. Cancels setInterval.
• handleEvent -- method of all objects with event handlers. Invokes the handler for the specified event.
• print -- window and frame method. Prints the contents of the window or frame.
• 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.
• setInterval -- window and frame method. 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.
• toString* -- converts the object or array to a literal. For this behavior, LANGUAGE="JavaScript1.2" must be specified in the <SCRIPT> tag.

Objects

• 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.

Operators

• 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, an object's property, or an element at a specified index in an array.

Properties

Function Property

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

Navigator Properties

• 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.

Window Properties

• innerHeight -- specifies the vertical dimension, in pixels, of the window's content area.
• innerWidth -- specifies the horizontal dimension, in pixels, of the window's content area.
• 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 bar 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

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. A global RegExp 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 the input which specifies the original input string against which the match was executed.

This section includes:

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

Signed Scripts

For additional power and functionality, scripts can now gain access to normally restricted information. This is achieved through signed scripts that request expanded privileges. This new functionality provides greater security than tainting.

Statements

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

Style Sheets

Using style sheets, you gain finer control over the presentation of your web pages. Navigator 4.0 supports two syntaxes for designing style sheets: Cascading Style Sheets (CSS) and JavaScript style sheets. CSS is the static approach to specifying style and JavaScript is the programmatic approach.

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

Miscellaneous

• You can add a button to the Personal Toolbar that, when clicked, activates a JavaScript command. toolbar. See Activating JavaScript Commands From the Personal Toolbar.

Compatibility With Earlier Versions of Navigator

As JavaScript evolves along with Navigator, its capabilities expand greatly. This means that JavaScript written for Navigator 4.0 may work in Navigator 4.0 only. To ensure that users of earlier versions of Navigator avoid problems when viewing pages that use JavaScript 1.2, use the LANGUAGE attribute in the <SCRIPT> tag to indicate which version of Javascript you're using. If you use LANGUAGE="JavaScript1.2", you need to be aware of the equality rules described below.

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.

By using the LANGUAGE attribute, you can write general JavaScript that Navigator version 2.0 and higher recognize, and include additional or refined behavior for newer versions of Navigator.