jQuery addClass example

Change class name on click in jQuery

HTML

<div id="banner-message">
 <a class="IndexImage" href="/forum/discussion/55/design-flaw-001-give-up"><img src="https://www.w3schools.com/w3css/img_lights.jpg" class="IndexImage" id="yourImg"></a>
  <button>Change image source</button>
</div>

JavaScript

var button = $("button")

button.on("click", function(){
   $('#yourImg').attr('src','https://www.w3schools.com/w3css/img_mountains.jpg');
})