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    This is an experimental technology, part of the ECMAScript 6 (Harmony) proposal.
    Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future version of browsers as the spec changes.


    The keys() method returns a new Iterator object that contains the keys for each element in the Map object in insertion order.




    Example: Using keys()

    var myMap = new Map();
    myMap.set("0", "foo");
    myMap.set(1, "bar");
    myMap.set({}, "baz");
    var mapIter = myMap.keys();
    console.log(; // "0"
    console.log(; // 1
    console.log(; // Object


    Specification Status Comment
    ECMAScript 6 (ECMA-262)
    The definition of 'Map.prototype.keys' in that specification.
    Draft Initial definition.

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support 38 20 (20) Not supported 25 7.1
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support Not supported 38 20.0 (20) Not supported Not supported iOS 8

    See also

    Document Tags and Contributors

    Contributors to this page: realityking, fscholz, arai
    Last updated by: arai,