What can't JavaScript programs do?

* use printers or other devices on the user's system or the client-side LAN (For a workaround, see Printing JavaScript output.) * directly access files on the user's system or the client-side LAN ; the only exception is the access to the browser's cookie files. (For a workaround, see the File Access section.) * directly access files on the Web server. (For a workaround, see the File Access section.) * implement multiprocessing or multithreading.