JavaScript 1.5; JScript 5.5; ECMAScript v3
o
Any object.
true if object is the prototype of o. Returns false if o is not an object or if object is not the prototype of o.
As explained in Chapter 8, JavaScript objects inherit properties from their prototype object. The prototype of an object is referred to by the prototype property of the constructor function used to create and initialize the object. The isPrototypeOf( ) method provides a way to determine if one object is the prototype of another. This technique can be used to determine the class of an object.
var o = new Object( ); // Create an object Object.prototype.isPrototypeOf(o) // true: o is an object Function.prototype.isPrototypeOf(o.toString); // true: toString is a function Array.prototype.isPrototypeOf([1,2,3]); // true: [1,2,3] is an array // Here is a way to perform a similar test (o.constructor == Object); // true: o was created with Object( ) constructor (o.toString.constructor == Function); // true: o.toString is a function // Prototype objects themselves have prototypes. The following call // returns true, showing that function objects inherit properties // from Function.prototype and also from Object.prototype. Object.prototype.isPrototypeOf(Function.prototype);