Summing of individual numbers in an array in JavaScript

Question

I'm trying to add up all the numbers in each array and print out the total sum of that array. I'm not sure how to get this code done.

Example:

var myArray = [123, 456, 789]

I want the program to print out 6,15,24.

Since 1+2+3 = 6, 4+5+6=15 and 7+8+9= 24.

How would I go about adding each individual number in that array?

Answer 1

You can use Array#map and Array#reduce.

With ES2015 Arrow Function syntax

myArray.map(el => el.toString().split('').reduce((sum, b) => sum + +b, 0));

var myArray = [123, 456, 789];

var resultArr = myArray.map(el => el.toString().split('').reduce((sum, b) => sum + +b, 0));

console.log(resultArr);
document.body.innerHTML = resultArr; // FOR DEMO ONLY

In ES5:

myArray.map(function (el) {
    return el.toString().split('').reduce(function (sum, b) {
        return sum + +b
    }, 0);
});

var myArray = [123, 456, 789];

var resultArr = myArray.map(function (el) {
    return el.toString().split('').reduce(function (sum, b) {
        return sum + +b
    }, 0);
});

console.log(resultArr);
document.body.innerHTML = resultArr;

Answer 2

You have to decompose each to number to its digits, you can use modulo operator for that.

For example, X mod 10 will always get the rightmost digit from X, and to remove the last digit of X you have to make an integer division, X div 10.

function parse(array) {
  return array.map(function(item) {
    var n = 0;
    while (item > 0) {
      n += item % 10;
      item = Math.floor(item/10);
    }

    return n;
  });
}