數組去重 Jquery

//去重
Array.prototype.unique = function(){
var res = [];
var json = {};
for(var i = 0; i < this.length; i++){
if(!json[this[i]]){
json[this[i]] = 1;
}else {
res.push(this[i]);
}
}
return res;
}
var arr = [1,2,1,2,1,4,5];
arr.unique