<pre class="shiki github-dark shaku"><code>// This is a JavaScript coding problem from BFE.dev /* type IsBad = (version: number) =&gt; boolean *//** * @param {IsBad} isBad */function firstBadVersion(isBad) { let counter = 0 return (version) =&gt; { if (!isBad(version)) return -1 while (counter &lt;= version) { if (!isBad(counter)) { counter += 1 continue } return counter } }}</code></pre>