JSFiddle - React, Tailwind, and code Playground

HTML

<div id="thisdiv" class="class1 class2 class3 class4 class5"> text </div>

JavaScript

$('#thisdiv').attr('class', function(i, v)
{
    var classes = v.split(' '),
        position = $.inArray('class3', classes);

    return classes.slice(0, position + 1).join(' ');
});

alert(  $('#thisdiv')[0].className);