Mozilla Developer NetworkTable of contents
Summary
Creates an object wrapper.
Syntax
new Object( [ value ] )
Parameters
- value
- Any value.
Description
The Object constructor creates an object wrapper for the given value. If the value is null or undefined, it will create and return an empty object, otherwise, it will return an object of a type that corresponds to the given value.
When called in a non-constructor context, Object behaves identically.
Properties
For properties available on Object instances, see Properties of Object instances.
- prototype
- Allows the addition of properties to all objects of type Object.
Methods
For methods available on Object instances, see Methods of Object instances.
create-
Requires JavaScript 1.8.5
Creates a new object with the specified prototype object and properties. defineProperty-
Requires JavaScript 1.8.5
Adds the named property described by a given descriptor to an object. defineProperties-
Requires JavaScript 1.8.5
Adds the named properties described by the given descriptors to an object. getOwnPropertyDescriptor-
Requires JavaScript 1.8.5
Returns a property descriptor for a named property on an object. keys-
Requires JavaScript 1.8.5
Returns an array containing the names of all of the given object's own enumerable properties. getOwnPropertyNames-
Requires JavaScript 1.8.5
Returns an array containing the names of all of the given object's own enumerable and non-enumerable properties. getPrototypeOf-
Requires JavaScript 1.8.1
Returns the prototype of the specified object. preventExtensions-
Requires JavaScript 1.8.5
Prevents any extensions of an object. isExtensible-
Requires JavaScript 1.8.5
Determine if extending of an object is allowed. seal-
Requires JavaScript 1.8.5
Prevents other code from deleting properties of an object. isSealed-
Requires JavaScript 1.8.5
Determine if an object is sealed. freeze-
Requires JavaScript 1.8.5
Freezes an object: other code can't delete or change any properties. isFrozen-
Requires JavaScript 1.8.5
Determine if an object was frozen.
Object instances
All objects in JavaScript are descended from Object; all objects inherit methods and properties from Object.prototype, although they may be overridden. For example, other constructors' prototypes override the constructor property and provide their own toString methods. Changes to the Object prototype object are propagated to all objects unless the properties and methods subject to those changes are overridden further along the prototype chain.
Properties
constructor- Specifies the function that creates an object's prototype.
__count__-
Obsolete since JavaScript 1.8.5
Returns the number of enumerable properties directly on a user-defined object. __parent__-
Obsolete since JavaScript 1.8.5
Points to an object's context. __proto__- Non-standard
Points to the object which was used as prototype when the object was instantiated.
Methods
__defineGetter__- Non-standard
Associates a function with a property that, when accessed, executes that function and returns its return value.
__defineSetter__- Non-standard
Associates a function with a property that, when set, executes that function which modifies the property.
eval-
Obsolete since JavaScript 1.8.5
Evaluates a string of JavaScript code in the context of the specified object. hasOwnProperty- Returns a boolean indicating whether an object contains the specified property as a direct property of that object and not inherited through the prototype chain.
isPrototypeOf- Returns a boolean indication whether the specified object is in the prototype chain of the object this method is called upon.
__lookupGetter__- Non-standard
Returns the function associated with the specified property by the__defineGetter__method.
__lookupSetter__- Non-standard
Returns the function associated with the specified property by the__defineSetter__method.
__noSuchMethod__- Non-standard
Allows a function to be defined that will be executed when an undefined object member is called as a method.
propertyIsEnumerable- Returns a boolean indicating if the internal ECMAScript DontEnum attribute is set.
toSource- Non-standard
Returns string containing the source of an object literal representing the object that this method is called upon; you can use this value to create a new object.
toLocaleString- Calls
toString.
toString- Returns a string representation of the object.
unwatch- Non-standard
Removes a watchpoint from a property of the object.
valueOf- Returns the primitive value of the specified object.
watch- Non-standard
Adds a watchpoint to a property of the object.
Examples
Example: Using Object given undefined and null types
The following examples store an empty Object object in o:
var o = new Object();
var o = new Object(undefined);
var o = new Object(null);
Example: Using Object to create Boolean objects
The following examples store Boolean objects in o:
// equivalent to o = new Boolean(true); var o = new Object(true);
// equivalent to o = new Boolean(false); var o = new Object(Boolean());
