<pre class="shiki github-dark shaku"><code>function getNthNum(n) { let str = "1"; function next(str) { let result = ""; let count = 1; for (let i = 1; i &lt;= str.length; i++) { if (str[i] === str[i - 1]) { count++; } else { result += count + str[i - 1]; count = 1; } } return result; } function generate(n, str) { if (n === 1) { return str; } return generate(n - 1, next(str)); } return generate(n, str);}</code></pre>