Answers for "group the numbers by 3 and sum javascript"

sum of all numbers in an array javascript

const arrSum = arr => arr.reduce((a,b) => a + b, 0)

two sum javascript solution

var twoSum = function(nums, target) {
  const indicies = {}
  
  for (let i = 0; i < nums.length; i++) {
    const num = nums[i]
    if (indicies[target - num] != null) {
      return [indicies[target - num], i]
    }
    indicies[num] = i
  }
};