The has()
method returns a boolean indicating whether an element with the specified key exists in the WeakMap
object or not.
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
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 |
---|
ECMAScript (ECMA-262) The definition of 'WeakMap.prototype.has' in that specification. |
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.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
has | Chrome Full support 36 | Edge Full support 12 | Firefox
Full support
6
| IE Full support 11 | Opera Full support 23 | Safari Full support 8 | WebView Android Full support 37 | Chrome Android Full support 36 | Firefox Android
Full support
6
| Opera Android Full support 24 | Safari iOS Full support 8 | Samsung Internet Android Full support 3.0 | nodejs
Full support
0.12
|
Legend
- Full support
- Full support
- See implementation notes.
- See implementation notes.
- User must explicitly enable this feature.
- User must explicitly enable this feature.