JSFiddle - React, Tailwind, and code Playground

HTML

<link href='http://fonts.googleapis.com/css?family=Gentium+Book+Basic' rel='stylesheet' type='text/css'>
<h2 style="text-align:left;" contenteditable="true">
    This is the title to bold
</h2>
<br />
<a id="boldIt" href="#">Bold selected text</a>

CSS

h2 {
    font-weight: 700;
}

JavaScript

document.execCommand("styleWithCSS", false, true);

$("#boldIt").on("click", function() {
 	document.execCommand('bold', false, null);   
});