JSFiddle - React, Tailwind, and code Playground

HTML

<span>Change Color</span>
<br>
<button>Click Me</button>
<p>Click the button</p>

CSS

.purple {
	color : purple;
}

JavaScript

function updateClass(element, newClass) {
	element.addClass(newClass);
	return true;
};

function makeCalculations() {
	$("p").text("Running...");

	var x = 0;
	for (var i = 0; i < 1000000000; i++) {
		x += i;
	}

	$("p").html("Done!" + "<br />" + "x = " + x);
}

$(function() {

	$("button").click(function() {

		updateClass($("span"), "purple").then(makeCalculations());
		
	});
	
});