instanceof special operatorS2C Home « Operators « instanceof

Prototype chain evaluation.

Description

The instanceof special operator tests whether an object has the prototype property of a constructor in its prototype chain.

Syntax


Signature Description
object instanceof constructorThe instanceof special operator tests whether an object has the prototype property of a constructor in its prototype chain.

Parameters


Parameter Description
objectThe object to test.
constructorThe constructor function to test for.

Examples

Following are examples of the instanceof special operator.


// The instanceof operator.
function A(){} // constructor 1 
function B(){} // constructor 2
var o1 = new A();  
var o2 = new B(); 
var anArray = new Array(5); 
anArray[0] = o1.constructor + " " + o2.constructor;
anArray[1] = o1 instanceof A; // true Object prototype chain  
anArray[2] = o2 instanceof A; // false (B.prototype not in A.prototype chain)  
anArray[3] = o1 instanceof Object; // all objects in Object prototype chain  
anArray[4] = o2 instanceof Object; // all objects in Object prototype chain  
alert(anArray); 


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Related Tutorials

JavaScript Basic Tutorials - Lesson 7 - Objects

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