JSFiddle - React, Tailwind, and code Playground

HTML

<div id="loading"><img src="http://jimpunk.net/Loading/wp-content/uploads/loading1.gif"/></div>
<button onclick="ShowLoadingGif()">ShowLoadingGif</button>

CSS

#loading
{
    display:none;
}

JavaScript

var Shown = false;
function ShowLoadingGif()
{
    $("#loading").show("fast",
                   function()
                   {
                        Shown = true;   
                   });
    while(!Shown)
    {
        //wait for callback to be executed
    }
    Shown = false;
}