Object.prototype.propertyIsEnumerable()

The propertyIsEnumerable() method returns a Boolean indicating whether the specified property is enumerable and is the object's own property.

Syntax

propertyIsEnumerable(prop)

Parameters

prop: The name of the property to test.

Return value

A true or false value indicating whether the specified property is enumerable and is the object's own property.

Description

Every object has a propertyIsEnumerable method. This method can determine whether the specified property in an object can be enumerated by a for...in loop, with the exception of properties inherited through the prototype chain. If the object does not have the specified property, this method returns false.

Note: Bear in mind that enumerable properties are looped over by for...in loops, with the exception of Symbols.

Examples

A basic use of `propertyIsEnumerable`

The following example shows the use of propertyIsEnumerable on objects and arrays:

var o = {};
var a = [];
o.prop = 'is enumerable';
a[0] = 'is enumerable';

o.propertyIsEnumerable('prop');   // returns true
a.propertyIsEnumerable(0);        // returns true

User-defined vs. built-in objects

The following example demonstrates the enumerability of user-defined vs. built-in properties:

var a = ['is enumerable'];

a.propertyIsEnumerable(0);          // returns true
a.propertyIsEnumerable('length');   // returns false

Math.propertyIsEnumerable('random');   // returns false
this.propertyIsEnumerable('Math');     // returns false

Direct vs. inherited properties

var a = [];
a.propertyIsEnumerable('constructor');         // returns false

function firstConstructor() {
  this.property = 'is not enumerable';
}

firstConstructor.prototype.firstMethod = function() {};

function secondConstructor() {
  this.method = function() { return 'is enumerable'; };
}

secondConstructor.prototype = new firstConstructor;
secondConstructor.prototype.constructor = secondConstructor;

var o = new secondConstructor();
o.arbitraryProperty = 'is enumerable';

o.propertyIsEnumerable('arbitraryProperty');   // returns true
o.propertyIsEnumerable('method');              // returns true
o.propertyIsEnumerable('property');            // returns false

o.property = 'is enumerable';

o.propertyIsEnumerable('property');            // returns true

// These return false as they are on the prototype which
// propertyIsEnumerable does not consider (even though the last two
// are iteratable with for-in)
o.propertyIsEnumerable('prototype');   // returns false (as of JS 1.8.1/FF3.6)
o.propertyIsEnumerable('constructor'); // returns false
o.propertyIsEnumerable('firstMethod'); // returns false

Specifications

Specification
ECMAScript Language Specification (ECMAScript) # sec-object.prototype.propertyisenumerable

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`propertyIsEnumerable`	1	12	1	5.5	4	3	1	18	4	10.1	1	1.0