JSFiddle - React, Tailwind, and code Playground

HTML

<p>Instead I want to display the list as</p>

<!-- where qtty is quantity -->
<li> 1 has a qtty x3 </li>
<li> 2 has a qtty x4 </li>

JavaScript

var list = [1,1,1,2,2,2,2]

var counts = {};
for (var i = 0; i < list.length; i++) {
    counts[list[i]] = 1 + (counts[list[i]] || 0);
}

alert('1 has a qtty x' + counts['1']);
alert('1 has a qtty x' + counts['2']);