multiplying-numbers-as-strings.js

const multiply = (a, b) => {
  const stack = [];
  a = a.split``.reverse();
  b = b.split``.reverse();
  
  for (let i = 0, la = a.length; i < la; i++) {
    for (let j = 0, lb = b.length; j < lb; j++) {
      const m = a[i] * b[j];
      const s = stack[i + j];
      stack[i + j] = s ? s + m : m;
    }
  }

  for (let i = 0, l = stack.length; i < l; i++) {
    const move = Math.floor(stack[i] / 10);
    stack[i] = stack[i] % 10;
    if (stack[i + 1]) stack[i + 1] += move;
    else if (move > 0) stack[i + 1] = move;
  }

  return stack.reverse().join``.replace(/^(0(?!$))+/, '');
}
//https://www.codewars.com/kata/multiplying-numbers-as-strings/javascript

/not my intent solution/
function multiply(a, b) {
const stack = [];
a = a.split.reverse(); b = b.split.reverse();

for (let i = 0, la = a.length; i < la; i++) {
for (let j = 0, lb = b.length; j < lb; j++) {
const m = a[i] * b[j];
const s = stack[i + j];
stack[i + j] = s ? s + m : m;
}
}

for (let i = 0, l = stack.length; i < l; i++) {
const move = Math.floor(stack[i] / 10);
stack[i] = stack[i] % 10;
if (stack[i + 1]) stack[i + 1] += move;
else if (move > 0) stack[i + 1] = move;
}

return stack.reverse().join``.replace(/^(0(?!$))+/, '');
}

function multiply(a, b) {return (BigInt(a) * BigInt(b)).toString()}