instanceof

Summary

Returns a Boolean value that indicates whether or not an object is an instance of a particular class.

Syntax

result = object instanceof class

result

Required. Any variable.

object

Required. Any object expression.

class

Required. Any defined object class.

Examples

The following example shows how to use the instanceof operator.

function objTest(obj){
     var i, t, s = "";
     t = new Array();
     t["Date"] = Date;
     t["Object"] = Object;
     t["Array"] = Array;
         for (i in t){
             if (obj instanceof t[i]) {
                 s += "obj is an instance of " + i + "<br/>";
             }
             else {
                 s += "obj is not an instance of " + i + "<br/>";
         }
     }
     return(s);
 }

 var obj = new Date();
 document.write(objTest(obj));

 // Output:
 // obj is an instance of Date
 // obj is an instance of Object
 // obj is not an instance of Array

Remarks

The instanceof operator returns true if object is an instance of class. It returns false if object is not an instance of class, or if object is null.

Attributions

• Microsoft Developer Network: Article