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Guru Tip: Avoid the HTML5 FOUJUI Experience

As I continue to incorporate more JavaScript into my applications and, especially, as I try to leverage the new JavaScript/HTML 5 technologies, I'm discovering a new problem: It's now possible for users to see raw, uninitialized HTML in their browser before my JavaScript properly arranges things. I asked Todd Anglin, VP for HTML5 Web & Mobile Tools at Telerik, if there was a solution to this problem. Here's what he said:

This is a new problem that can ruin the fancy, new experience of your HTML5 app. I think of it as FOUJI, or Flash of Uninitialized JavaScript UI: Users see the ugly HTML briefly and then, suddenly, the page looks right. One solution for this problem is to use a JavaScript loading screen that "hides" the page HTML as it initializes.

For instance, this HTML displays some gif (probably animated) that lets users know that their page is being prepared:

<div id="preLoad">
  <div>
    <img src="styles/BlueOpal/loading-image.gif"  alt="Loading Image"
 style="width:48px;" />
    <br />Loading...
  </div>
</div>
I use it with this CSS:
#preLoad{            
    width:100%;
    height:100%;
    background:#FFF;
    position:absolute;
    top:0;    
}        
 
#preLoad div{
    position:absolute;
    top: 50%;
    left: 50%;
    height:60px;
    margin-top: -30px;
    margin-left: -24px;
}

To make the loading screen "go away" when I've finished setting it up, I trigger a new event when the JavaScript that initializes my page is complete:

$(document).trigger("APP_READY");
In my main page, I wire up code to that event to hide my loading screen:
$(document).bind("APP_READY",function(){ 
    $("#preLoad").fadeOut(); 
});

Now users see the loading screen until my app finishes initializing. Then the loading screen fades out to reveal the UI -- without FOUJUI.

The richness of HTML5 Web apps is great, but it includes extra challenges like FOUJUI as you make the transition to the client. One of the things that we're doing with the Kendo UI is provide another solution: server-side helpers that render the HTML on the server before sending it to the user. In the meantime, you have to check your apps for any unintended flashing.

Todd had more to say on improving this solution (including incorporating CSS3 Transitions) on his blog.

Posted by Peter Vogel on 03/25/2012 at 1:16 PM


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