A function to return indices of the elements that sums equal to the target number

indices.js

function foo(nums, target) {
  const indices = {};

  for (let i = 0; i < nums.length; i++) {
    const rem = target - nums[i];

    if (indices[rem] !== undefined) return [indices[rem], i];

    indices[nums[i]] = i;
  }
}

# Time complexity: O(n)

foo([2,3,4], 6) => [0,2]
foo([3,2,4], 6) => [1,2]
foo([3,4,11,15], 7) => [0,1]