Two Sum

var twoSum = function(nums, target) {
    var len = nums.length,
        i = 0,
        hash = {},
        res = [],
        t1, t2;

    while (i < len) {
        t1 = target - nums[i];
        t2 = nums[i];
        if (hash[t1] != undefined) {
            res.push(hash[t1]);
            res.push(i + 1);
            break;
        }
        if (hash[t2] == undefined) {
            hash[t2] = i + 1;
        }
        i++;
    }

    return res;
};

var nums = [2, 7, 11, 15];
console.log(twoSum(nums, 9));