<pre class="shiki github-dark shaku"><code>/*type Callback = (error: Error, data: any) =&gt; voidtype AsyncFunc = ( callback: Callback, data: any) =&gt; void*//** * @param {AsyncFunc[]} funcs * @return {(callback: Callback) =&gt; void} */const promisify = fun =&gt; input =&gt; new Promise((res,rej)=&gt;{ fun((error,data)=&gt;error?rej(error):res(data),input);})function parallel(funcs) { return function(cb,data){ Promise.all(funcs.map(fun=&gt;promisify(fun)(data))) .then(outputs=&gt;cb(undefined,outputs)) .catch(error=&gt;cb(error,undefined)); }}// function parallel(funcs) {// let res = [], cnt = 0, hasError = false;// return function run(cb, result) {// funcs.forEach((fn, index) =&gt; {// fn((error, data) =&gt; {// if (hasError) return;// if (error) {// hasError = true;// cb(error, undefined);// return;// }// res[index] = data;// cnt++;// if (cnt === funcs.length) {// cb(undefined, res);// }// })// })// }// }</code></pre>

my 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…