The has() method returns a boolean indicating whether an element with the specified key exists in the WeakMap object or not.
WeakMap.prototype.has()
Try it
Syntax
has(key)
Parameters
-
key -
Required. The key of the element to test for presence in the
WeakMapobject.
Return value
- Boolean
-
Returns
trueif an element with the specified key exists in theWeakMapobject; 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
Browser compatibility
| Desktop | Mobile | Server | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
has |
36
|
12
|
6
Before 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.
|
11
|
23
|
8
|
37
|
36
|
6
Before 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.
|
24
|
8
|
3.0
|
1.0
|
0.12.0
0.10.0
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap/has
