Binary Sum & multiply

binarySumMultiply.js

function sum(x, y){
  if(y === 0) return x
  
  return sum( x^y, (x&y)<<1 )
}



function multiply(x, y){
  if(x ===0 || y ===0) return 0
  let ans = 0
  let shifts = 0
  
  while(x){
    if(x & 1) ans = sum(ans, y << shifts)
    shifts++
    x = x >> 1
  }
  
  return ans
}