The WeakSet
object lets you store weakly held objects in a collection.
Syntax
new WeakSet([iterable]);
Parameters
- iterable
- If an iterable object is passed, all of its elements will be added to the new
WeakSet
. null is treated as undefined.
Examples
Using the WeakSet object
var ws = new WeakSet(); var obj = {}; var foo = {}; ws.add(window); ws.add(obj); ws.has(window); // true ws.has(foo); // false, foo has not been added to the set ws.delete(window); // removes window from the set ws.has(window); // false, window has been removed
Description
WeakSet
objects are collections of objects. An object in the WeakSet
may only occur once; it is unique in the WeakSet
's collection.
The main differences to the Set
object are:
- In contrast to
Sets
,WeakSets
are collections of objects only and not of arbitrary values of any type. - The
WeakSet
is weak: References to objects in the collection are held weakly. If there is no other reference to an object stored in theWeakSet
, they can be garbage collected. That also means that there is no list of current objects stored in the collection.WeakSets
are not enumerable.
Properties
WeakSet.length
- The value of the
length
property is 0. WeakSet.prototype
- Represents the prototype for the
Set
constructor. Allows the addition of properties to allWeakSet
objects.
WeakSet
instances
All WeakSet
instances inherit from WeakSet.prototype
.
Properties
WeakSet.prototype.constructor
- Returns the function that created an instance's prototype. This is the
WeakSet
function by default.
Methods
WeakSet.prototype.add(value)
- Appends a new object with the given value to the
WeakSet
object. WeakSet.prototype.delete(value)
- Removes the element associated to the
value
.WeakSet.prototype.has(value)
will returnfalse
afterwards. WeakSet.prototype.has(value)
- Returns a boolean asserting whether an element is present with the given value in the
WeakSet
object or not. WeakSet.prototype.clear()
Removes all elements from theWeakSet
object.
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'WeakSet' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of 'WeakSet' in that specification. |
Living Standard |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 36 | 12 | 34 | No | 23 | 9 |
new WeakSet(iterable) | 38 | 12 | 34 | No | 25 | 9 |
new WeakSet(null) | Yes | 12 | 37 | No | ? | 9 |
add | 36 | Yes | 34 | No | 23 | 9 |
clear | 36 — 43 | No | 34 — 46 | No | 25 — 30 | No |
delete | 36 | Yes | 34 | No | 23 | 9 |
has | 36 | Yes | 34 | No | 23 | 9 |
prototype | 36 | Yes | 34 | No | 23 | 9 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | 36 | 36 | 12 | 34 | No | 23 | 9 |
new WeakSet(iterable) | 38 | 38 | 12 | 34 | No | 25 | 9 |
new WeakSet(null) | Yes | Yes | 12 | 37 | No | ? | 9 |
add | 36 | 36 | Yes | 34 | No | 23 | 9 |
clear | 36 — 43 | 36 — 43 | No | 34 — 46 | No | 25 — 30 | No |
delete | 36 | 36 | Yes | 34 | No | 23 | 9 |
has | 36 | 36 | Yes | 34 | No | 23 | 9 |
prototype | 36 | 36 | Yes | 34 | No | 23 | 9 |
See also
Document Tags and Contributors
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chrisdavidmills,
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Last updated by:
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