<pre class="shiki github-dark shaku"><code>// This is a JavaScript coding problem from BFE.dev /** * @typedef {(version: number) =&gt; boolean} IsBad *//** * @param {IsBad} isBad * @return {(v: number) =&gt; number} */function firstBadVersion(isBad) {	// firstBadVersion receive a check function isBad // and should return a closure which accepts a version number(integer) return (version) =&gt; { // write your code to return the first bad version // if none found, return -1 let high = version; let low = 0; while (low &lt;= high) { let mid = Math.floor((low + high) /2) if (isBad(mid)) { high = mid - 1; } else { low = mid + 1; } } return isBad(low) ? low : -1; }}</code></pre>