JavaScript & jQuery Tutorials

JS Home Right Arrow JS Reference Right Arrow instanceof

instanceof special operator

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); 

Press the button below to action the above code:



  

go to home page Homepage go to top of page Top