1  'use strict';
 2  
 3  var toString = Object.prototype.toString
 4  
 5    , id = toString.call('');
 6  
 7  module.exports = function (x) {
 8  	return (typeof x === 'string') || (x && (typeof x == 'object') &&
 9  		((x instanceof String) || (toString.call(x) === id))) || false;
10  };