raptor-polyfill/object/keys.js

Polyfills for various EcmaScript 5 and EcmaScript 6 methods distributed as CommonJS modules that can be require'd individually or as a whole.

// ES5 15.2.3.14
// http://es5.github.com/#x15.2.3.14
if (!Object.keys) {
    var _hasOwnProperty = Object.prototype.hasOwnProperty;

    // http://whattheheadsaid.com/2010/10/a-safer-object-keys-compatibility-implementation
    var hasDontEnumBug = true,
        dontEnums = [
            "toString",
            "toLocaleString",
            "valueOf",
            "hasOwnProperty",
            "isPrototypeOf",
            "propertyIsEnumerable",
            "constructor"
        ],
        dontEnumsLength = dontEnums.length;

    /*jshint unused:false*/
    for (var key in {"toString": null}) {
        hasDontEnumBug = false;
    }

    Object.keys = function keys(object) {

        if ((typeof object != "object" && typeof object != "function") || object === null) {
            throw new TypeError("Object.keys called on a non-object");
        }

        var _keys = [];
        for (var name in object) {
            if (_hasOwnProperty.call(object, name)) {
                _keys.push(name);
            }
        }

        if (hasDontEnumBug) {
            for (var i = 0, ii = dontEnumsLength; i < ii; i++) {
                var dontEnum = dontEnums[i];
                if (_hasOwnProperty.call(object, dontEnum)) {
                    _keys.push(dontEnum);
                }
            }
        }
        return _keys;
    };

}