Q:

Cross platform Files APIs - Open and list folders

I'm going to start this mozilla student project: https://github.com/Mozilla-Student-Projects/Projects-Tracker/issues/54 
I'm a little confused about the WebAPIs, because as far as I know, it's not possible to manage files with JS. 
Someone can point me the right direction to research and test??
I enabled the Firefox DeviceStorage, but I'm not able to getDeviceStorage, the status keeps on 'pending'.
Thx

A:

If you're working on an MDN summer project, you should start here! 
https://developer.mozilla.org/en/docs/Web/API/File
The summer school thread that you've linked to is looking for a browser app, so I think you'd use the File API to browse for MP3s - here's a fiddle showing it working with an MP3 - 
http://jsfiddle.net/derickbailey/s4P2v/ 
I've patched this fiddle here:
http://jsfiddle.net/s4P2v/129/
with autoplay="true" so that it actually plays the MP3.
html...
<audio id="audio" autoplay="true"></audio>

js....
$("#audio").prop("src", objectUrl);

Using the File API, you could use the info to write multiple audio tags - https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_HTML5_audio_and_video - one per MP3 file.
The audio tags would would then let you play the files... and you have the beginnings of an MP3 player. 

