[javascript] How to display a "busy" indicator with jQuery?

Old thread, but i wanted to update since i worked on this problem today, i didnt have jquery in my project so i did it the plain old javascript way, i also needed to block the content on the screen so in my xhtml

    <img id="loading" src="#{request.contextPath}/images/spinner.gif" style="display: none;"/>

in my javascript

    document.getElementsByClassName('myclass').style.opacity = '0.7'
    document.getElementById('loading').style.display = "block";