<pre class="shiki github-dark shaku"><code>/** * Question to clarify - * 1. will it compare premitives via == or === * 2. will it go in nested level for non primitives * 3. does order matters for isEqual in object *//**| * Requirement * 1. it should be able to take two params * 2. if both param are of same type, compare them * 3. *//** * Thought process * 1. compare their type- if different type, return false * 2. if same type, and if primitive, do === * 3. if same tyep and non-primitive, * - for arrays, check length first. * - then loop through arrays and compare each element by recursive cal * - for objets, check their size * - then loop through each property. both key &amp; value should match by recusive call *//** * @param {any} a * @param {any} b * @return {boolean} *//** * Polyfill for lodash isEqual to deeply compare two values (primitives, arrays, or objects) * @param {any} a - First value to compare * @param {any} b - Second value to compare * @return {boolean} - Returns true if a and b are deeply equal, false otherwise */function isEqual(a, b, visited = new Map()) { // your code here // // below type check is not required // if (typeof a !== typeof b) { // return false; // } // Directly compare primitives and identical references if (typeof a !== "object" &amp;&amp; typeof b !== `object`) { return a === b; } // Handle circular references // if the object has circular ref, and if it has been visited, return true // else add it in visited list if (visited.has(a) || visited.has(b)) return true; visited.set(a, b); // for arrays if (Array.isArray(a) &amp;&amp; Array.isArray(b)) { // check lenght if (a.length !== b.length) { return false; } // a.forEach((aValue, aIndex)=&gt;{ // if (isEqual(a[aIndex], b[aIndex], visited) === false) { // return false; // } // }) // return true; // ifz̄ all are deep equal return a.every((el, i) =&gt; isEqual(el, b[i], visited)); // clean // for (let i = 0; i &lt; a.length; i++) { // if (isEqual(a[i], b[i], visited) === false) { // return false; // } // } } // for objects if ( Object.prototype.toString.call(a) === "[object Object]" &amp;&amp; Object.prototype.toString.call(b) === "[object Object]" ) { // check their sizze if (Object.keys(a).length !== Object.keys(b).length) { return false; } for (const [key, value] of Object.entries(a)) { // match keys, if this key does not exist in 2nd object if (!b[key]) { return false; } // match vlaue if (isEqual(value, b[key], visited) === false) { return false; } } return true; } // return false for any other data type return false;}</code></pre>

soluton with explanation by Krishna saini

Google

_.isEqual is useful when you want to compare complex data types by value not the reference. Can you implement your own version of deep equal isEqual? …