text: Object.keys = (function() {
  	'use strict';
  
  	// modified from https://github.com/es-shims/object-keys
  
  	var has = Object.prototype.hasOwnProperty;
  	var toStr = Object.prototype.toString;
  	var isEnumerable = Object.prototype.propertyIsEnumerable;
  	var hasDontEnumBug = !isEnumerable.call({ toString: null }, 'toString');
  	var hasProtoEnumBug = isEnumerable.call(function () {}, 'prototype');
  	var dontEnums = [
  		'toString',
  		'toLocaleString',
  		'valueOf',
  		'hasOwnProperty',
  		'isPrototypeOf',
  		'propertyIsEnumerable',
  		'constructor'
  	];
  	var equalsConstructorPrototype = function (o) {
  		var ctor = o.constructor;
  		return ctor && ctor.prototype === o;
  	};
  	var excludedKeys = {
  		$console: true,
  		$external: true,
  		$frame: true,
  		$frameElement: true,
  		$frames: true,
  		$innerHeight: true,
  		$innerWidth: true,
  		$outerHeight: true,
  		$outerWidth: true,
  		$pageXOffset: true,
  		$pageYOffset: true,
  		$parent: true,
  		$scrollLeft: true,
  		$scrollTop: true,
  		$scrollX: true,
  		$scrollY: true,
  		$self: true,
  		$webkitIndexedDB: true,
  		$webkitStorageInfo: true,
  		$window: true
  	};
  	var hasAutomationEqualityBug = (function () {
  		/* global window */
  		if (typeof window === 'undefined') { return false; }
  		for (var k in window) {
  			try {
  				if (!excludedKeys['$' + k] && has.call(window, k) && window[k] !== null && typeof window[k] === 'object') {
  					try {
  						equalsConstructorPrototype(window[k]);
  					} catch (e) {
  						return true;
  					}
  				}
  			} catch (e) {
  				return true;
  			}
  		}
  		return false;
  	}());
  	var equalsConstructorPrototypeIfNotBuggy = function (o) {
  		/* global window */
  		if (typeof window === 'undefined' || !hasAutomationEqualityBug) {
  			return equalsConstructorPrototype(o);
  		}
  		try {
  			return equalsConstructorPrototype(o);
  		} catch (e) {
  			return false;
  		}
  	};
  
  	function isArgumentsObject(value) {
  		var str = toStr.call(value);
  		var isArgs = str === '[object Arguments]';
  		if (!isArgs) {
  			isArgs = str !== '[object Array]' &&
  				value !== null &&
  				typeof value === 'object' &&
  				typeof value.length === 'number' &&
  				value.length >= 0 &&
  				toStr.call(value.callee) === '[object Function]';
  		}
  		return isArgs;
  	}
  
  	return function keys(object) {
  		var isFunction = toStr.call(object) === '[object Function]';
  		var isArguments = isArgumentsObject(object);
  		var isString = toStr.call(object) === '[object String]';
  		var theKeys = [];
  
  		if (object === undefined || object === null) {
  			throw new TypeError('Cannot convert undefined or null to object');
  		}
  
  		var skipProto = hasProtoEnumBug && isFunction;
  		if (isString && object.length > 0 && !has.call(object, 0)) {
  			for (var i = 0; i < object.length; ++i) {
  				theKeys.push(String(i));
  			}
  		}
  
  		if (isArguments && object.length > 0) {
  			for (var j = 0; j < object.length; ++j) {
  				theKeys.push(String(j));
  			}
  		} else {
  			for (var name in object) {
  				if (!(skipProto && name === 'prototype') && has.call(object, name)) {
  					theKeys.push(String(name));
  				}
  			}
  		}
  
  		if (hasDontEnumBug) {
  			var skipConstructor = equalsConstructorPrototypeIfNotBuggy(object);
  
  			for (var k = 0; k < dontEnums.length; ++k) {
  				if (!(skipConstructor && dontEnums[k] === 'constructor') && has.call(object, dontEnums[k])) {
  					theKeys.push(dontEnums[k]);
  				}
  			}
  		}
  		return theKeys;
  	};
  }());
  