The has()
method returns a boolean indicating whether an element with the specified key exists in the WeakMap
object or not.
Syntax
wm.has(key);
Parameters
- key
- Required. The key of the element to test for presence in the
WeakMap
object.
Return value
- Boolean
- Returns
true
if an element with the specified key exists in theWeakMap
object; otherwisefalse
.
Examples
Using the has
method
var wm = new WeakMap(); wm.set(window, 'foo'); wm.has(window); // returns true wm.has('baz'); // returns false
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'WeakMap.prototype.has' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of 'WeakMap.prototype.has' 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 | Yes | 61 | 11 | 23 | 8 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | 36 | 36 | Yes | 61 | 11 | 23 | 8 |
1. Prior to Firefox 38, this method threw a TypeError
when the key parameter was not an object. This has been fixed in version 38 and later to return false
as per the ES2015 standard.