SOURCE

var twoSum = function(nums, target) {
    for(let i = 0;i<nums.length;i++){
        for(let k=i+1;k<nums.length;k++){
            if(nums[i]+nums[k]==target){
                return [i,k]
            }
        }
    }
};

console.log(twoSum([2, 7, 11, 15],9))