javascript - How to force the HTML5 Audio tag to reload a (changing) file

Question

I have a bit of code in javascript that generates a wav file and then attaches it to a button so it can be played:

function makeWav(){        
            $.get(("../testsound/getsound.pl?text="+document.myform.outputtext.value));
setTimeout(callback, 500);
            return false;
        }
function callback() {
var audio = new Audio('http://www.joereddington.com/testsound/hope.wav');
audio.load();
audio.play();
           //     $("#player").html("<embed src=http://www.joereddington.com/testsound/hope.wav autostart=true  >");
        }

Obviously the hope.wav file changes very regularly. But my problem is that only the first .wav to be generated is played unless I completely reload the site each time. How do I make the (presumably) callback function go and get a new version of the .wav rather than the cache?

EDIT: Works fine on the iPad - I'm having this problem in firefox.

Answer 1

You can't directly control the caching from within your JavaScript. Retrieving files is the responsibility of the browser, which is why you're getting different results on different browsers.

When a web server sends a file to the browser, it also sends some headers with extra details about that file. One of them is the Cache-Control header, which tells the browser if the file is cacheable. Sending a Cache-Control: no-cache header should stop browsers caching the file, and make subsequent requests retrieve the file from your server.

On Apache, you can use an .htaccess file or a <Directory> rule in your server configuration to change the caching for files in the /testsound directory. Put the following in /testsound/.htaccess:

<ifModule mod_headers.c>
    Header set Cache-Control no-cache
</ifModule>

---

Another technique is to include a "cache-busting" parameter in your request. Your web server is serving a static file - but your web browser doesn't know that. For all it knows, a request for /testsound/hope.wav?cb=foo could return a completely different file to a request for /testsound/hope.wav?cb=bar. Thus, if you include an always-changing parameter in your web request, the browser won't find it in its cache and it will retrieve the new file. A timestamp is a good choice:

function callback() {
  var url = "http://www.joereddington.com/testsound/hope.wav?cb=" + new Date().getTime();
  var audio = new Audio(url);
  audio.load();
  audio.play();        
}