javascript 数组去重

1     //去重
2     var hash_already_input = {};
3     for (var i in arr_already_input) {
4         hash_already_input[arr_already_input[i]] = arr_already_input[i];
5     }
6     arr_already_input = [];
7     for (key in hash_already_input) {
8         arr_already_input.push(key);
9     }