JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
<div class="block-item" style="width:10px"></div>
<div class="block-item" style="width:50px"></div>
<div class="block-item" style="width:90px"></div>
<div>

JavaScript

var totalWidth = 0;

$('.block-item').each(function(index) {
    totalWidth += parseInt($(this).width());
});

alert("Total Width is " + totalWidth);