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The Object.getOwnPropertyNames()
method returns an array of all properties (including non-enumerable properties except for those which use Symbol) found directly in a given object.
Syntax
Object.getOwnPropertyNames(obj)
Parameters
obj
- The object whose enumerable and non-enumerable properties are to be returned.
Return value
An array of strings that corresponds to the properties found directly in the given object.
Description
Object.getOwnPropertyNames()
returns an array whose elements are strings corresponding to the enumerable and non-enumerable properties found directly in a given object obj
. The ordering of the enumerable properties in the array is consistent with the ordering exposed by a for...in
loop (or by Object.keys()
) over the properties of the object. The ordering of the non-enumerable properties in the array and the ordering among the enumerable properties is not defined.
Examples
Using Object.getOwnPropertyNames()
var arr = ['a', 'b', 'c']; console.log(Object.getOwnPropertyNames(arr).sort()); // logs ["0", "1", "2", "length"] // Array-like object var obj = { 0: 'a', 1: 'b', 2: 'c' }; console.log(Object.getOwnPropertyNames(obj).sort()); // logs ["0", "1", "2"] // Logging property names and values using Array.forEach Object.getOwnPropertyNames(obj).forEach( function (val, idx, array) { console.log(val + ' -> ' + obj[val]); } ); // logs // 0 -> a // 1 -> b // 2 -> c // non-enumerable property var my_obj = Object.create({}, { getFoo: { value: function() { return this.foo; }, enumerable: false } }); my_obj.foo = 1; console.log(Object.getOwnPropertyNames(my_obj).sort()); // logs ["foo", "getFoo"]
If you want only the enumerable properties, see Object.keys()
or use a for...in
loop (note that this will also return enumerable properties found along the prototype chain for the object unless the latter is filtered with hasOwnProperty()
).
Items on the prototype chain are not listed:
function ParentClass() {} ParentClass.prototype.inheritedMethod = function() {}; function ChildClass() { this.prop = 5; this.method = function() {}; } ChildClass.prototype = new ParentClass; ChildClass.prototype.prototypeMethod = function() {}; console.log( Object.getOwnPropertyNames( new ChildClass() // ["prop", "method"] ) );
Get non-enumerable properties only
This uses the Array.prototype.filter()
function to remove the enumerable keys (obtained with Object.keys()
) from a list of all keys (obtained with Object.getOwnPropertyNames()
) thus giving only the non-enumerable keys as output.
var target = myObject; var enum_and_nonenum = Object.getOwnPropertyNames(target); var enum_only = Object.keys(target); var nonenum_only = enum_and_nonenum.filter(function(key) { var indexInEnum = enum_only.indexOf(key); if (indexInEnum == -1) { // Not found in enum_only keys, // meaning that the key is non-enumerable, // so return true so we keep this in the filter return true; } else { return false; } }); console.log(nonenum_only);
Notes
In ES5, if the argument to this method is not an object (a primitive), then it will cause a TypeError
. In ES2015, a non-object argument will be coerced to an object.
Object.getOwnPropertyNames('foo'); // TypeError: "foo" is not an object (ES5 code) Object.getOwnPropertyNames('foo'); // ["0", "1", "2", "length"] (ES2015 code)
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript Latest Draft (ECMA-262) The definition of 'Object.getOwnPropertyNames' in that specification. |
Draft | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Object.getOwnPropertyNames' in that specification. |
Standard | |
ECMAScript 5.1 (ECMA-262) The definition of 'Object.getOwnPropertyNames' in that specification. |
Standard | Initial definition. Implemented in JavaScript 1.8.5. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
getOwnPropertyNames | Chrome Full support 5 | Edge Full support 12 | Firefox Full support 4 | IE Full support 9 | Opera Full support 12 | Safari Full support 5 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Legend
- Full support
- Full support
Firefox-specific notes
Prior to Firefox 28, Object.getOwnPropertyNames
did not see unresolved properties of Error
objects. This has been fixed in later versions (bug 724768).