Bitwise addition

add.js

// Fuck the addition operator. Real programmers work in binary!
function add(a, b) {
  // XOR to get the sum of the bits
  var sum = a ^ b;

  // "Carry" bits are common to both numbers
  var carry = (a & b) << 1;

  if (sum & carry) {
    // Rinse and repeat until there are no leftover bits
    return add(sum, carry);
  } else {
    return sum ^ carry;
  }
}


/*
> add(5, 6)
11
> add(5, 10)
15
> add(-1, 40)
39
> add(1, 9)
10
*/

Thank you so much for this - I found you from Google and have been working on this problem for a while. Working through B2B SWE's video:
https://www.youtube.com/watch?v=qq64FrA2UXQ

adding 1234567890 + 1234567890 causes it to return a minus number. What could be the cause?
By the way, 123456789 + 123456789 works just fine.

@ozgursar this function is only correct for numbers where the sum is equal to or less than 2147483647 (the maximum signed 32-bit integer).

> add(2147483647, 0)
< 2147483647

> add(2147483647, 1)
< -2147483648

@wildlyinaccurate thank you. I tried to split the input numbers into smaller parts to be able to sum larger numbers but it computes incorrectly.