The propertyIsEnumerable()
method returns a Boolean indicating whether the specified property is enumerable.
Syntax
obj.propertyIsEnumerable(prop)
Parameters
prop
- The name of the property to test.
Return value
A Boolean
indicating whether the specified property is enumerable.
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
.
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 method() { 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 | Status | Comment |
---|---|---|
ECMAScript 3rd Edition (ECMA-262) | Standard | Initial definition |
ECMAScript 5.1 (ECMA-262) The definition of 'Object.prototype.propertyIsEnumerable' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Object.prototype.propertyIsEnumerable' in that specification. |
Standard | |
ECMAScript Latest Draft (ECMA-262) The definition of 'Object.prototype.propertyIsEnumerable' in that specification. |
Living Standard |
Browser compatibility
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | Yes | Yes | Yes |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | Yes | Yes | Yes | Yes |