js-sum-without-a-plus

js-sum-without-a-plus.js

/**
 * @param {number} a
 * @param {number} b
 * @return {number}
 */
var getSum = function(a, b) {
  var result = a;
  var rest = b;
  while (rest)  {
    var carry = result & rest; // and (to get carry value: 0 || 1)
    result = result ^ rest; // xor (real sum)
    rest = carry << 1; //carry shift (increase by multiplying, same as: carry * 2, thats why we have a +1 effect here)
  }
  return result;
};