The add() method appends a new object to the end of a WeakSet object.

Syntax

ws.add(value);

Parameters

value
Required. The object to add to the WeakSet collection.

Return value

The WeakSet object.

Using the add method

var ws = new WeakSet();

ws.add(window); // add the window object to the WeakSet

ws.has(window); // true

// Weakset only takes objects as arguments
ws.add(1);
// results in "TypeError: Invalid value used in weak set" in Chrome
// and "TypeError: 1 is not a non-null object" in Firefox

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'WeakSet.prototype.add' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'WeakSet.prototype.add' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 36Edge Full support YesFirefox Full support 34IE No support NoOpera Full support 23Safari Full support 9WebView Android Full support 37Chrome Android Full support 36Edge Mobile Full support YesFirefox Android Full support 34Opera Android Full support 23Safari iOS Full support 9Samsung Internet Android Full support Yesnodejs Full support 0.12

Legend

Full support  
Full support
No support  
No support

See also

Document Tags and Contributors

Last updated by: wbamberg,