JSFiddle - React, Tailwind, and code Playground

HTML

<div contenteditable="true" class="textEditor">Some random text.</div>

<a href="#" class="embolden">Bold</a>

CSS

.bold {
    font-weight: bold;
}

JavaScript

jQuery(function($) {
    $('.embolden').click(function(){
        $( ".textEditor" ).toggleClass( "bold" );
    });
});