Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

JavaScript objectsJavaScript 1.0; JScript 1.0; ECMAScript v1

Constructor

new Object( )new
Object(value)

Arguments

value

This optional argument specifies a primitive JavaScript value -- a
number, boolean, or string -- that is to be converted to a Number,
Boolean, or String object. This object is not supported prior to
JavaScript 1.1 and ECMAScript v1.

Returns

If no value argument is passed, this
constructor returns a newly created Object instance. If a primitive
value argument is specified, the
constructor creates and returns a Number, Boolean, or String object
wrapper for the primitive value. When the Object(
) constructor is called as a function, without the
new operator, it behaves just as it does when used
with the new operator.

Properties

constructor

A reference to the JavaScript function that was the constructor for
the object.

Methods

hasOwnProperty( )

Checks whether an object has a locally defined (noninherited)
property with a specified name.

isPrototypeOf( )

Checks whether this object is the prototype object of a specified
object.

propertyIsEnumerable( )

Checks whether a named property exists and would be enumerated by a
for/in loop.

toLocaleString( )

Returns a localized string representation of the object. The default
implementation of this method simply calls toString(
), but subclasses may override it to provide localization.

toString( )

Returns a string representation of the

object. The implementation of this
method provided by the Object class is quite generic and does not
provide much useful information. Subclasses of Object typically
override this method by defining their own toString(
) method which produces more useful output.

valueOf( )

Returns the primitive value of the object, if any. For objects of
type Object, this method simply returns the object itself. Subclasses
of Object, such as Number and Boolean, override this method to return
the primitive value associated with the object.

Description

The Object class is a built-in data type
of the JavaScript language. It serves as the superclass for all other
JavaScript objects; therefore, methods and behavior of the Object
class are inherited by all other objects. The basic behavior of
objects in JavaScript is explained in Chapter 8.

In addition to the Object( ) constructor shown
above, objects can also be created and initialized using the Object
literal syntax described in Chapter 8.

See Also

Array, Boolean, Function, Function.prototype, Number, String; Chapter 8