JSFiddle - React, Tailwind, and code Playground

HTML

<div id="overlay">&nbsp;</div>
<div id="result">Results goes here</div>
<button>Update</button>

CSS

#overlay {
    position: absolute;
    background-color:#000;
    width: 100%;
    height: 100%;
    opacity: .5;
    filter: alpha(opacity=50);
    z-index: 100;
    display: none;
}

JavaScript

$("button").click(function() {
    $("#overlay").stop(false, true).animate({
        opacity: 'show'
    }, 200);

    var res = $.ajax({
        type: "GET",
        dataType: "json",
        url: "/echo/json/",
        async: false
    }).responseText;

    $("#result").html(res);

    $("#overlay").stop(false, true).animate({
        opacity: 'hide'
    }, 200);
});