e - sum_all_except_index.js

// Given an array of integers, return a new array such that each element at index i of the new array is the product of all the numbers in the original array except the one at i.

// For example, if our input was [1, 2, 3, 4, 5], the expected output would be [120, 60, 40, 30, 24]. If our input was [3, 2, 1], the expected output would be [2, 3, 6].

const sumAllButIndex = (arr) => {
  const result = [];

  for (let i = 0; i < arr.length; i++) {
    result.push(arr.reduce((p, c, y) => (y !== i ? p * c : p), 1));
  }

  return result;
};

console.log(sumAllButIndex([1, 2, 3, 4, 5]));