JSFiddle - React, Tailwind, and code Playground

HTML

<img src="http://d3sdoylwcs36el.cloudfront.net/VEN-virtual-enterprise-network-business-opportunities-small-fish_id799929_size485.jpg" id="ImageButton1" onclick="javascript:showLoad();" />
<img src="http://www.pennystockalerts.com/wp-content/uploads/2009/12/small-cap.jpg" id="ImageButton2" alt="Get Last Digits" style="display:none;" />
<img src="http://1.bp.blogspot.com/_xn2gmPb9TfM/SBZwjqwS6MI/AAAAAAAABZw/uMVQlcxlosA/s400/loading-icon.gif" id="LoadingImg" style="display:none;" />

JavaScript

function showLoad() {
    document.getElementById('ImageButton1').src=document.getElementById('LoadingImg').src;
   
    setTimeout(swapImageSrc, 1000);
}

function swapImageSrc() {
    document.getElementById('ImageButton1').src = document.getElementById('ImageButton2').src;
  
}