<pre class="shiki github-dark shaku"><code>// copied from lib.es5.d.tsdeclare interface Array&lt;T&gt; { myMap&lt;U&gt;(callbackfn: (value: T, index: number, array: T[]) =&gt; U, thisArg?: any): U[];}Array.prototype.myMap = function(callback, thisArg) { const length = this.length const result = new Array(length) for (let i = 0; i &lt; length; i++) { if (i in this) { result[i] = callback.call(thisArg, this[i], i, this) } } return result}</code></pre>

(TypeScript) Attention to the sparse Array and altering on the fly

Apple

Amazon

Please implement your own Array.prototype.map(). [1,2,3].myMap(num => num * 2) > please avoid using Array.prototype.map() directly in your code.…