js数组去重的hash方法

if (!Array.prototype.unique) {
 Array.prototype.unique = function () {
 var hash = {}, result = [], item;
 for (var i = 0; i < this.length; i++) {
 item = this[i];
 if ( !hash[item] ) {
 hash[item] = true;
 result.push(item);
 }
 }
 return result;
 };
}

var arr = [0, 1, '1', true, 5, true, false, undefined, undefined, null, null];
arr.unique();

if (!Array.prototype.unique) {
 Array.prototype.unique = function () {
 var hash = {}, result = [], type = '', item;
 for (var i = 0; i < this.length; i++) {
 item = this[i];
 type = Object.prototype.toString.call(item);

 if ( !hash[item + type] ) {
 hash[item + type] = true;
 result.push(item);
 }
 }
 return result;
 };
}