code: function bitwise(str){
  	var hash = 0;
  	if (str.length == 0) return hash;
  	for (var i = 0; i < str.length; i++) {
  		var ch = str.charCodeAt(i);
  		hash = ((hash<<5)-hash) + ch;
  		hash = hash & hash; // Convert to 32bit integer
  	}
  	return hash;
  }
docs: refer to: http://werxltd.com/wp/2010/05/13/javascript-implementation-of-javas-string-hashcode-method/