Big strings multiplication

multiply-strings.js

/**
 * @param {string} num1
 * @param {string} num2
 * @return {string}
 */
var multiply = function(num1, num2) {
    if(num1 === "0" || num2 === "0") {
        return "0";
    }
    const numbers = Array.from({length: num2.length}, _ => "0");
    for(let i = num2.length - 1; i >= 0; i--) {
        numbers[i] = [];
        for(let x = 0; x < num2.length - i - 1; x++) {
            numbers[i].push("0");
        }
        const m = Number(num2[i]);
        let carry = "0";
        for(let j = num1.length - 1; j >= 0; j--) {
            const n = Number(num1[j]);
            const mn = (m * n) + Number(carry);
            carry = (Math.floor(mn / 10)).toString();
            const nn = (mn%10).toString();
            console.log({m, n, mn, carry, nn});
            numbers[i].push(nn);
        }
        numbers[i].push(carry);
    }
    let sum = [];
    let carry = 0;
    for(let i = 0; i < num2.length + num1.length; i++) {
        let s = 0;
        
        for(let j = 0; j < numbers.length; j++) {
            s += Number(numbers[j][i] || "0");
        }
        s += carry;
        carry = Math.floor(s/10);
        s %= 10;
        sum[i] = s;
    }
    console.log(numbers, sum);
    if(sum[sum.length - 1] === 0) {
        sum.pop();
    }
    
    return sum.reverse().join('');
};