JSFiddle - React, Tailwind, and code Playground

HTML

<div id="a" style="background:red;width:100px;height:100px"></div>
<div id="b" style="background:green;width:100px;height:100px"></div>
<div id="c" style="background:blue;width:100px;height:100px"></div>
<div id="d" style="background:yellow;width:100px;height:100px"></div>
<button type="button" id="btn">START</button>
<button type="button" id="btn2">RESET</button>

JavaScript

$('#btn').click(function() {
    $('#a').fadeTo('fast', 0, function() {

        // The below will not work
        $('#a').fadeTo('fast', 1);
    });
    $('#b').fadeTo('fast', 0, function() {
    });
    $('#c').fadeTo('fast', 0);
    $('#d').fadeTo('fast', 0);
});

$('#btn2').click(function() {
    $('#a').queue([]).css({
        opacity: 1
    });
    $('#b').queue([]).css({
        opacity: 1
    });
    $('#c').queue([]).css({
        opacity: 1
    });
    $('#d').queue([]).css({
        opacity: 1
    });
});