JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main-client-block selector righted setwidth200"></div>

JavaScript

$("div").each(function () {
    var check = "setwidth";
    var classes = $(this).attr("class").split(/\s+/);
    var width = 0;
    $.each(classes, function (index, item) {
        if (item.indexOf(check) === 0) 
            width = parseInt(item.substr(check.length), 10);
    });

    console.log(width);
});