Preventing HTML5 applicationCache checking event on offline application load

Question

I have an HTML5/jquery mobile web app at http://app.bluedot.mobi . It is used for long distance races to track competitors via SPOT satellite tracking. The issue I have not yet resolved is that when loading the app when no data connection exists, the browser throws a "no data connection" alert popup as it is attempting to fetch the manifest during the checking event. Even when a data connection is present, loading the app can take a very long time. There are ~ 500 files to check. The fastest way to load the app (from a phone) is to be in airplane mode and dismiss the browser's alert - not so elegant.

Rather than force an update on users who tend to be in the backcountry with a spotty connection, I want to use applicationCache.update() programmatically, giving the user control over the process and speeding up app load whether on or offline.

Is this currently possible with the HTML5 spec and respective browser implementations?

Answer 1

Sounds like you need the abort() method. Unfortunately it is very new, and it will probably be a while before it is implemented by the majority of mobile browsers.

Answer 2

There are ~ 500 files to check.

It sounds like you're implying that the browser checks each file to see if there's any of them which has changed. This is not correct. The browser only checks the manifest file if that has changed, and that is a simple byte check. If the manifest file has not changed, the browser believes nothing has changed.

So if your application is slow to start, it might be your because your application is complex and there's alot of HTML and Javascript to parse. I would advise you to take a look at the application and see if there's anything you can optimize. In that case, you might want to take a look at Yahoo's Best Practices for Speeding Up Your Web Site page.

For example, I noticed you have a lot of Javascript code in the HEAD section. The beforementioned article advices us to move all Javascript (To the extent of what's possible) to the bottom of the page, so that the browser can start rendering the page as soon as possible. And there's a lot of other sound advice in the article. So take a look, I'm sure you'll find it useful. :-)