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Objects

This section describes the following new objects and changes to existing objects:

• arguments
• event
• Array (links to a different page)
• Number
• the regular expression object
• RegExp
• screen
• String (links to a different page)

In addition, objects can now be creating using literal notation.

Creating Objects With Literal Notation

In addition to creating an object using its constructor function, you can create it using literal notation.

Syntax

objectName = {property1:value1, property2:value2,..., propertyn:valuen}

Properties

objectName is the name of the new object

propertyn is a property.

valuen is the value assigned to the propertyn.

Description

JavaScript interprets objects created through literal notation once only, when the HTML page is loaded.

Example

The following example creates myHonda with three properties. Note that the engine property is also an object with its own properties.

myHonda = {color:"red",wheels:4,engine:{cylinders:4,size:2.2}}

arguments

Core object. The arguments array object provides information about a function at the time the function is invoked. In previous JavaScript versions, arguments provided a list of indexed elements and a length property. In JavaScript 1.2, arguments includes these additional properties:

• formal arguments -- each formal argument of a function is a property of the arguments array.
• local variables -- each local variable of a function is a property of the arguments array.
• caller -- a property whose value is the arguments array of the outer function. If there is no outer function, the value is undefined.
• callee -- a property whose value is the function reference.

For example, the following script demonstrates several of the arguments properties;

<SCRIPT> 

function b(z) { 
  document.write(arguments.z + "<BR>") 
  document.write (arguments.caller.x + "<BR>") 
  return 99 
} 

function a(x, y) { 
     return  b(534) 
}

document.write (a(2,3) + "<BR>") 

</SCRIPT>

This writes:

534
2
99

534 is the actual parameter to b, so it is the value of arguments.z

2 is a's actual x parameter, so (viewed within b) it is the value of arguments.caller.x.

99 is what a(2,3) returns.

Number

Core object. Number(x) now produces NaN rather than an error if x is a string that does not contain a well-formed numeric literal. For example,

x=Number("three");
document.write(x + "<BR>");

prints NaN

screen

Client-side object. Contains information about the display screen resolution and colors.

Syntax

screen.propertyName

Parameters

propertyName is one of the properties listed below.

Property of

None

Properties

Methods

None

Event handlers

None