Two Sum

 1 var twoSum = function(nums, target) {
 2     var len = nums.length,
 3         i = 0,
 4         hash = {},
 5         res = [],
 6         t1, t2;
 7 
 8     while (i < len) {
 9         t1 = target - nums[i];
10         t2 = nums[i];
11         if (hash[t1] != undefined) {
12             res.push(hash[t1]);
13             res.push(i + 1);
14             break;
15         }
16         if (hash[t2] == undefined) {
17             hash[t2] = i + 1;
18         }
19         i++;
20     }
21 
22     return res;
23 };
24 
25 var nums = [2, 7, 11, 15];
26 console.log(twoSum(nums, 9));