Loading external files for a non-hosted HTML5 application

Question

I am currently developing a HTML5 game which loads in an external resource. Currently, I am using XMLHttpRequest to read in the file, but this does not work on Chrome, resulting in a

XMLHttpRequest cannot load file:///E:/game/data.txt
Cross origin requests are only supported for HTTP.

The file is in the same directory as the HTML5 file.

Questions:

1. Is there any way for a HTML5 application to use XMLHttpRequest (or other method) to load in an external file without requiring it to be hosted on a webserver?

2. If I package the HTML5 code as an application on a tablet/phone which supports HTML5, would XMLHttpRequest be able to load external files?

Answer 1

1. (a) Yes and no. As a matter of security-policy, XHR has traditionally been both same-protocol (ie: http://, rather than file:///), and on top of that, has traditionally been same-domain, as well (as in same subdomain -- http://pages.site.com/index can't get a file from http://scripts.site.com/). Cross-domain requests are now available, but they require a webserver, regardless, and the server hosting the file has to accept the request specifically.

   (b) So in a roundabout way, the answer is yes, some implementations might (incorrectly) allow you to grab a file through XHR, even if the page is speaking in file-system terms, rather than http requests (older versions of browsers)... ...but otherwise you're going to need a webserver of one kind or another. The good news is that they're dirt-simple to install. EasyPHP would be sufficient, and it's pretty much a 3-click solution. There are countless others as well. It's just the first that comes to mind in terms of brain-off installation, if all you want is a file-server in apache, and you aren't planning on using a server-side scripting language (or if you do plan on using PHP).

2. XMLHttpRequest would absolutely be able to get external files...
   IF they're actually external (ie: not bundled in a phone-specific cache -- use the phone's built-in file-access API for that, and write a wrapper to handle each one with the same, custom interface), AND the phone currently has reception -- be prepared to handle failure-conditions (like having a default-settings object, or having error-handling or whatever the best-case is, for whatever is missing).

   Also, look into Application Cache Manifests. Again, this is an html5 solution which different versions of different phones handle differently (early-days versus more standardized formats). DO NOT USE IT DURING DEVELOPMENT, AS IT MAKES TESTING CODE/CONTENT CHANGES MISERABLY SLOW AND PAINFUL, but it's useful when your product is pretty much finished and bug-free, and seconds away from launch, where you tell users' browsers to cache all of the content for eternity, so that they can play offline, and they can save all kinds of bandwidth, not having to download everything the next time they play.