JSFiddle - React, Tailwind, and code Playground
by _sir
HTML
<h3>Take an array and return the number of unique duplicates in it</h3>
<p>
<strong>Your answer should be: </strong>0, 1, 2
</p>
<div id="output"></div>
JavaScript
var arr = [[1, 2, 3],[1, 1, 2, 3],[1, 2, 2, 3, 3, 3]];
document.getElementById("output").innerHTML = '';