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JavaScript Programmer’s Reference Property attributes: ReadOnly, DontDelete, DontEnum. Cross-references: ECMA 262 edition 2 section 15.2.3.1 ECMA 262 edition 2 section 15.2.4 ECMA 262 edition 3 section 15.2.3.1 Object.toLocaleString() (Method) Returns a string primitive version of the object taking the present locale into account during the translation. Availability: ECMAScript edition 3 JavaScript 1.5 JScript 5.5 Internet Explorer 5.5 Netscape 6.0 Property/method value type: String primitive JavaScript syntax: -myObject.toLocaleString() The locale context supplies some special conversion rules for strings. Depending on the locale, this might include special characters or a means of using double byte characters. It may also affect the direction of the text, for certain Asian locales for example. Warnings: . The ECMA standard reserves the first argument of this method for future use. It does not specify what that is but warns against implementations extending the syntax to include its use. Cross-references: ECMA 262 edition 3 section 15.2.4.3 Object.toSource() (Method) Output a string describing the object contents. Availability: JavaScript 1.3 JScript 3.0 Internet Explorer 4.0 Netscape 4.06 Property/method value type: String primitive JavaScript syntax: -myObject.toSource() 1586

O Object.prototype (Property) Object objects inherit the following properties from the Object.prototype: . Object.constructor . Object.prototype Object objects inherit the following methods from their prototype: . Object.toString() . Object.valueOf() The prototype property for the Object prototype object is null. The example demonstrates how to provide extensions to all instances of this class by adding a function to the prototype object. Warnings: . This is not supported on the WebTV platform. Example code: See also: Arguments object, Function.arguments[], JellyScript, Object object, Object(), Object.constructor, Object.toString(), Object.valueOf(), prototype property 1585

JavaScript Programmer’s Reference Objects are identified either by the NAME=” “HTML tag attribute or by the ID=” ” HTML tag attribute. Netscape shows a marginal preference for the name property while MSIE seems slightly better disposed towards the ID property. However in many cases, both browsers support either technique and in some cases will locate items named with either tag as if they existed in a single namespace. See also: NAME=”…” Object.propertyIsEnumerable() (Method) A test for whether a property has the don’t enumerate flag set or not. Availability: Property/method value type: JavaScript syntax: Argument list: If the receiving object has a member property of the name that is passed in the argument, and if the DontEnumattribute of that property is false, then this method returns the Boolean true value. Cross-references: ECMA 262 edition 3 section 15.2.4.7 Object.prototype (Property) The prototype for the Objectobject, which can be used to extend the interface for all Object objects. ECMAScript edition 3 JavaScript 1.5 JScript 5.5 Internet Explorer 5.5 Netscape 6.0 Boolean primitive -myObject.propertyIsEnumerable(aName) aName The name of the object property to test Availability: ECMAScript edition 2 JavaScript 1.1 JScript 3.0 Internet Explorer 4.0 Netscape 3.0 Opera browser 3.0 Property/method value type: Object object -Object.prototype JavaScript syntax: -myObject.constructor.prototype The initial value of the prototype property of an Objectobject is the built in Object prototype object. 1584

O Object.isPrototypeOf() (Method) This method would be useful if it could test for the existence of a property in the inheritance chain. There is an internal HasProperty()method but the ECMA standard indicate that it is not exposed to the script interface. See also: HasProperty() Cross-references: ECMA 262 edition 3 section 15.2.4.5 Object.isPrototypeOf() (Method) A test for the relationship between two objects to ascertain direct parentage. Availability: Property/method value type: JavaScript syntax: Argument list: The receiving object is tested for identity against the object referred to by the prototype property of the object passed as an argument. If the object in the argument is a direct child object through the prototype chain, then this method returns a true value. ECMAScript edition 3 JavaScript 1.5 JScript 5.5 Internet Explorer 5.5 Netscape 6.0 Boolean primitive -myObject.isPrototypeOf(anObject) anObject The object whose prototype is to be tested See also: HasInstance() Cross-references: ECMA 262 edition 3 section 15.2.4.6 Object.name (Property) This corresponds to the NAME attribute of the tag that creates the object. Availability: JScript 5.5 Internet Explorer 5.5 Property/method value type: String primitive JavaScript syntax: IE myObject.name 1583

JavaScript Programmer’s Reference Cross-references: ECMA 262 edition 2 section 15.2.4.1 ECMA 262 edition 3 section 15.2.2 Object.eval() (Method) Evaluate the JavaScript source text passed in a string argument. Availability: JavaScript 1.1 JScript 3.0 Internet Explorer 4.0 Netscape 3.0 Netscape Enterprise Server version 2.0 Opera browser 3.0 Deprecated Property/method value type: Function result JavaScript syntax: -myObject.eval() Warnings: . This is now deprecated and may even be unavailable in recent versions of Netscape and JScript. You should use the eval() function available from the global object. See also: eval() Object.hasOwnProperty() (Method) A method that can be used to test whether a property exists and belongs to the receiving object. Availability: Property/method value type: JavaScript syntax: Argument list: For this method to yield a Boolean truevalue, the property named in the argument must exist and must belong to the receiving object. If the property is inherited from a prototype or earlier ancestor then this method returns false. 1582 ECMAScript edition 3 JavaScript 1.5 JScript 5.5 Internet Explorer 5.5 Netscape 6.0 Boolean primitive -myObject.hasOwnProperty(aName) aName The name of a property to test for

O Object.Class (Property/internal) Object.Class (Property/internal) Internal property that returns an object class. Availability: ECMAScript edition 2 This is an internal property that describes the class that an Object object instance is a member of. The reserved words suggest that in the future, this property may be externalized. See also: Class, Object object Property attributes: DontEnum, Internal. Cross-references: ECMA 262 edition 2 section 8.6.2 ECMA 262 edition 2 section 15.2.2.1 ECMA 262 edition 3 section 8.6.2 Object.constructor (Property) A reference to a constructor object. Availability: ECMAScript edition 2 JavaScript 1.1 JScript 1.0 Internet Explorer 3.02 Netscape 3.0 Opera browser 3.0 Property/method value type: Object object JavaScript syntax: -myObject.constructor The initial value of the Object.prototype.constructor is the built-in Object constructor. You can use this as one way of creating objects although it is more popular to use the new Object() technique. This property is useful if you have an object that you want to clone but you don’t know what sort of object it is. Simply access the constructor belonging to the object you have a reference to. Netscape provides constructors for many objects, virtually all of them in fact, even when it is highly inappropriate to do so. MSIE is far more selective and there are some occasions when you might wish for a constructor that MSIE does not make available. See also: Object literal, Object.prototype 1581

JavaScript Programmer’s Reference Object.__parent__ (Property) A special property in which to access the scope chain during function execution. JavaScript 1.2 ScopeChain object Availability: Netscape 4.0 Property/method value type: JavaScript syntax: N myObject.__parent__ See also: Lexical scoping, __parent__ Object.__proto__ (Property) A special property in which to access the prototype inheritance chain during construction. JavaScript 1.2 Function object Availability: Netscape 4.0 Property/method value type: JavaScript syntax: N myObject.__proto__ See also: Lexical scoping, Prototype Based Inheritance, Prototype chain, __proto__ Object.assign() (Method) A deprecated mechanism for intercepting messages sent to objects. JavaScript 1.1 Availability: Netscape 3.0 Deprecated JavaScript syntax: myObject.assign() N Warnings: . This method is deprecated in favor of the Object.watch()and Object.unwatch() methods. See also: Object.unwatch(), Object.watch() 1580

O Object() (Function) Object() (Function) An Object object constructor. Object(aValue) - aValue A value to be stored in the new object. Argument list: The Object Constructor can be called as a function. When this happens, the value passed in undergoes a type conversion. In an ECMA-compliant implementation, the Object constructor function uses the ToObject conversion. However it handles input values undefined and null as special cases and creates a new object as if the constructor had been used with the new operator. The table summarizes the results based on the input value data types. Availability: ECMAScript edition 2 JavaScript 1.1 JScript 1.0 Internet Explorer 3.02 Netscape 3.0 Property/method value type: An object of a type that depends on the passed in argument -Object() JavaScript syntax: Value Result No argument Creates a new empty object as if new Object()had been called. null Creates a new empty object as if new Object(null) had been called. undefined Creates a new empty object as if new Object(undefined)had been called. Boolean Create a new boolean object whose default value is the input value. Number Create a new number object whose default value is the input value. String Create a new string object whose default value is the input value. Object No conversion, the input value is returned unchanged. See also: Cast operator, Constructor function, constructor property, Implicit conversion, Object object Cross-references: ECMA 262 edition 2 section 15.1.1 ECMA 262 edition 2 section 15.1.3.1 ECMA 262 edition 2 section 15.2.2.2 ECMA 262 edition 3 section 15.2 1579

JavaScript Programmer’s Reference Unless you assign the result of the new operation, an object will simply consume memory. You need to store a reference to it at the time it is instantiated. You can do this by assigning it to a variable or a property of another object, passing it in to a function and making sure it gets retained in there, or storing it as an element in an array. Warnings: . You can refer to objects without the parentheses but then you are not referring to a constructor function but to the object itself. The behavior varies between browsers and depends on the kind of object being instantiated and probably depends on whether it is a wrapper for a primitive data type or a more complex aggregated type. . These all appear to create the same kind of object in both MSIE and Netscape myObject = Object(); myNewObject = new Object(); myOtherObject = new Object; These do not: myBoolean = Boolean(); myNewBoolean = new Boolean(); myOtherBoolean = new Boolean; . In the case of the Boolean, Number, and String object types, only the first form will initialize the new object with a value. Placing the result of these examples in document.write() statements illustrates the behavior. You may want to examine the objects returned in more detail by developing an object inspector script. See also: Boolean(), Constructor function, constructor property, Garbage collection, Global object, Memory leak, new, Number(), Object constant, Object object, Object.prototype, Reference counting, String() Cross-references: ECMA 262 edition 2 section 15.1.1 ECMA 262 edition 2 section 15.1.3.1 ECMA 262 edition 2 section 15.2.2.2 ECMA 262 edition 3 section 15.2.2 1578

O Object() (Constructor) ECMA 262 edition 3 section 10.1.5 ECMA 262 edition 3 section 15.2 O’Reilly JavaScript Definitive Guide page 44 Wrox Instant JavaScript page 28 Object() (Constructor) An Object object constructor. Availability: ECMAScript edition 2 JavaScript 1.1 JScript 3.0 Internet Explorer 4.0 Netscape 3.0 Netscape Enterprise Server 2.0 Opera 3.0 Property/method value type: Object object -new Object -new Object() JavaScript syntax: -new Object(aValue) Argument list: aValue An initial value for the new object When Object is called as part of a new expression, it is a constructor that may create an object instance. There are limitations what is sensible for the newoperator to be able to do with the Object constructor. Since the Objectis considered to be the highest ancestor of all objects in the prototype inheritance chain, you cannot logically have more than one Object object. Passing other native objects to the ObjectConstructor implies a type casting from their native object type to the Object type. That’s not logical either. The main use of the Object Constructor then is to manufacturer object instantiations from non-object data types. The table summarizes the resulting values from using the Object() constructor with the new operator. No argument Creates a new empty object null Creates a new empty object undefined Creates a new empty object Boolean Create a new boolean object whose default value is the input value Number Create a new number object whose default value is the input value String Create a new string object whose default value is the input value Native object Return the native object itself Host object Host implementation dependant behavior. Objects are cloned if necessary but some may not be Value Result 1577