Adding a loading mask to your ExtJS application

Adding a loading mask like the one on the ExtJS API application is a nice way of showing the user that something is happening while their browser downloads the source code. It’s also extremely easy to do.

First, place the following HTML above all of your javascript include tags, ideally just after the <body> tag:

&lt;div id=&quot;loading-mask&quot;&gt;&lt;/div&gt;
&lt;div id=&quot;loading&quot;&gt;
  &lt;div class=&quot;loading-indicator&quot;&gt;
    Loading...
  &lt;/div&gt;
&lt;/div&gt;

If you are currently including javascript files inside the <head>, don’t – put them at the bottom.

With a bit of CSS (see below), this provides a white mask over all underlying content, and a loading message. When everything has loaded, remove the mask like this:

Ext.onReady(function() {
  setTimeout(function(){
    Ext.get('loading').remove();
    Ext.get('loading-mask').fadeOut({remove:true});
  }, 250);
});

The above simply fades out the HTML elements to reveal the now ready page. The setTimeout call gives your app a little time to render, which is useful if you’re doing something like pulling external content down from the server.

Finally, here’s the CSS I use to style up the loading mask. You’ll need to download a loading image and stick it in the appropriate directory.

#loading-mask {
  position: absolute;
  left:     0;
  top:      0;
  width:    100%;
  height:   100%;
  z-index:  20000;
  background-color: white;
}

#loading {
  position: absolute;
  left:     50%;
  top:      50%;
  padding:  2px;
  z-index:  20001;
  height:   auto;
  margin:   -35px 0 0 -30px;
}

#loading .loading-indicator {
  background: url(../images/loading.gif) no-repeat;
  color:      #555;
  font:       bold 13px tahoma,arial,helvetica;
  padding:    8px 42px;
  margin:     0;
  text-align: center;
  height:     auto;
}
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