<pre class="shiki github-dark shaku"><code>// This is a JavaScript coding problem from BFE.dev type IsBad = (version: number) =&gt; booleanfunction firstBadVersion(isBad: IsBad) {	// firstBadVersion receive a check function isBad // and should return a closure which accepts a version number(integer) function getFirstBadVersion(num: number): number { if(isBad(num) &amp;&amp; isBad(num-1)) { return getFirstBadVersion(num-1) } return num; } return (version: number): number =&gt; { // write your code to return the first bad version // if none found, return -1 if(isBad(version)) { return getFirstBadVersion(version) } return -1 }}</code></pre>