Concept
<ul>
<li>higher order function(function returning a function): returning functions allows for the creation of specialized functions, it can also create a closure(closure = comb a function within lexical environment)</li>
<li><code>new Promise((resolve, reject)=&gt; {})</code>: <code>resolve</code> and <code>reject</code> are the callback functions,</li>
<li><code>Promise.resolve()</code> static methods resolve the given value, if the value is a promise that promise is return (make it fulfills to a non-thenable value.)
Intuition</li>
</ul>
Return a new promise, only use the resolve callback once each of the value of promises is resolved, and reject in catch or <code>then(onFulfilled, onRejected)</code>. Iterate through the promises, and store them in original order and use the <code>resolvedCounter</code> to keep in track
<pre class="shiki github-dark shaku"><code>/** * @param {Array&lt;any&gt;} promises - notice input might have non-Promises * @return {Promise&lt;any[]&gt;} * Intuition: * Return a new promise for two reject and resolve callback * pendingCounter to track the * Promise.resolve(promises[i]) * .then(val=&gt;{ * result[i] = val * }).catch(rej) */function all(promises) { // your code here return new Promise((res, rej)=&gt;{ const ans = []; if (promises.length === 0) { return res(ans); } let pendingCounter = promises.length; for (let i = 0; i &lt; promises.length; i++){ Promise .resolve(promises[i]) .then(val =&gt; { ans[i] = val; pendingCounter--; if (pendingCounter === 0) { return res(ans) } }) .catch(rej) } })}</code></pre>

Iterative approach: using Promise(), Promise.resolve().then().catch(),

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> The Promise.all() method takes an iterable of promises as an input, and returns a single Promise that resolves to an array of the results of the inp…