<pre class="shiki github-dark shaku"><code>const promisify = fn =&gt; input =&gt; new Promise((res, rej) =&gt; { fn((err, output) =&gt; err ? rej(err) : res(output), input)})function parallel(fns) { return (cb, input) =&gt; { Promise .all(fns.map(fn =&gt; promisify(fn)(input))) .then(outputs =&gt; cb(undefined, outputs)) .catch(err =&gt; cb(err, undefined)) }}</code></pre>

This is my accepted solution

This problem is related to 29. implement async helper - sequence(). You are asked to implement an async function helper, parallel() which works like P…