JSFiddle - React, Tailwind, and code Playground

HTML

<div class="moduletable_menu">
    <div class="tog">
        <h3>Main Menu</h3>
    </div>
    <div class="cont">
        <ul class="menu">Menu Form</ul>
    </div>
</div>
<div class="moduletable_menu">
    <div class="tog">
        <h3>Newsletter</h3>
    </div>
    <div class="cont">
        Newsletter form
    </div>
</div>

CSS

.highlight {
    font-weight: bold;
    background-color: #CCC;
}

JavaScript

var modules = $$('.cont');
modules.each(function(module) {
    var toggle = module.getPrevious('div.tog');
    var heading = toggle.getElement('h3');
    heading.addClass('highlight');
    // this gets the heading text
    alert(heading.getText());
});