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    WeakMap.prototype.has()

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    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 the WeakMap object; otherwise false.

    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 2017 Draft (ECMA-262)
    The definition of 'WeakMap.prototype.has' in that specification.    		 Draft  

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support 36 6.0 (6.0) 11 23 7.1
    Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support No support 6.0 (6.0) No support No support 8

    Firefox-specific notes

    • Prior to SpiderMonkey 38 (Firefox 38 / Thunderbird 38 / SeaMonkey 2.35), 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 latest ES6 standard (bug 1127827).

    See also

    Etiquetas y colaboradores del documento

    Etiquetas: 
     Colaboradores en esta página: fscholz, realityking
     Última actualización por: fscholz,