title: how to change the CSS background-image of a class-pseudoelement by Javascript only?
body: <p>I'm getting nowhere with this. I have an element, which is using a :before pseudo selector. </p>
  
  <p>CSS is like this:</p>
  
  <pre><code> .initHandler:before { 
        width: 100%; 
        position: absolute; 
        top: 0; 
        bottom: 0; 
        left: 0; 
        right: 0; 
        display: block; 
        height: 110%; 
        z-index: 999999;  
        background-color: white; /*background:white  url(../images/ajax-loader.gif) no-repeat center center;*/    
        content: "initializing..."; 
        text-align: center; 
        font-color: #ccc; 
        line-height: 150px; 
        vertical-align: bottom; 
        }
  </code></pre>
  
  <p>This gives me a white background for my app, which is loading "behind the curtain". On iOS I'm using a startup image, which I'm setting in the page head <code>before</code> jquery and jquerymobile are loaded.</p>
  
  <p>I now want to change the background of my <code>initHaendler:before</code> element to the determined iOS splashscreen.</p>
  
  <p>However I need to this in pure javascript and I have no idea how to select a class/pseudoelement to set a css value.</p>
  
  <p>Can someone help out?</p>
  
  <p>Thanks!</p>