<pre class="shiki github-dark shaku"><code>/** * @param {string} num1 * @param {string} num2 * @return {string} */function add(num1, num2) { let buffer = 0; const result = []; let num1Idx = num1.length - 1; let num2Idx = num2.length - 1; while(num1Idx &gt;= 0 || num2Idx &gt;= 0 || buffer !== 0) { const digit1 = num1Idx &gt;= 0 ? parseInt(num1[num1Idx], 10) : 0; const digit2 = num2Idx &gt;= 0 ? parseInt(num2[num2Idx], 10) : 0; const ariphmeticResult = buffer + digit1 + digit2; buffer = ariphmeticResult &gt;= 10 ? 1 : 0; result.unshift(ariphmeticResult % 10) num1Idx--; num2Idx--; } return result.join('');}</code></pre>

Simply and lovely

Luckily we have BigInt in JavaScript so handle big numbers. What if we need to do it by ourselves for older browsers? You are asked to implement a str…