This only works in google chrome:
<input type="file" webkitdirectory>
This will prompt the user to select a directory and you can then access the files
property of the input to see the contained files.
It is then possible to use the File System API to construct a virtual, sandboxed file system of the user selected files and have programmatic access to this virtual filesystem as if it was a real filesystem accessed by desktop app.
There is no way otherwise because that would be a big security issue
Working demo in google chrome: http://jsfiddle.net/JwgqC/
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