in

Summary

Tests for the existence of a property in an object.

Syntax

result = property in object

result

Required. Any variable.

property

Required. An expression that evaluates to a string expression.

object

Required. Any object.

Examples

The following example shows how to use the in operator:

// Create an object that has some properties.
 var myObject = new Object();
 myObject.name = "James";
 myObject.age = "22";
 myObject.phone = "555 0234";

 if ("phone" in myObject)
    document.write ("property is present");
 else
    document.write ("property is not present");

 // Output: property is present

Remarks

The in operator determines whether an object has a property named property. It also determines whether the property is part of the object’s prototype chain. For more information about object prototypes, see Prototypes and Prototype Inheritance.

Attributions

• Microsoft Developer Network: Article