Javascript: Object keys polyfill

object-keys-polyfill.js

/**
 * Polyfill for Object.keys
 *
 * @see: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/keys
 */
if (!Object.keys) {
  Object.keys = (function () {
    var hasOwnProperty = Object.prototype.hasOwnProperty,
        hasDontEnumBug = !({toString: null}).propertyIsEnumerable('toString'),
        dontEnums = [
          'toString',
          'toLocaleString',
          'valueOf',
          'hasOwnProperty',
          'isPrototypeOf',
          'propertyIsEnumerable',
          'constructor'
        ],
        dontEnumsLength = dontEnums.length;
 
    return function (obj) {
      if (typeof obj !== 'object' && typeof obj !== 'function' || obj === null) throw new TypeError('Object.keys called on non-object');
 
      var result = [];
 
      for (var prop in obj) {
        if (hasOwnProperty.call(obj, prop)) result.push(prop);
      }
 
      if (hasDontEnumBug) {
        for (var i=0; i < dontEnumsLength; i++) {
          if (hasOwnProperty.call(obj, dontEnums[i])) result.push(dontEnums[i]);
        }
      }
      return result;
    }
  })()
};

@austinhinderer: MIT, see the source.

What license is this code available under? BSD? MIT? Apache?

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