<div id="game"></div>
<script type="text/javascript">
    EJS_player = '#game';
    EJS_gameUrl = '/your/game/rom.zip';
    EJS_core = 'snes9x';
</script>
<script src="js/vendor/jquery.min.js"></script>
<script src="js/vendor/jquery.hotkeys.js"></script>
<script src="js/vendor/browserfs.min.js"></script>
<script src="js/libretro.js"></script>

Simply extract the release into the root of your webserver and try this test page for the snes9x emulator.

Supported emulators

bluemsx- https://github.com/libretro/blueMSX-libretro
fceumm- https://github.com/libretro/libretro-fceumm
gambatte- https://github.com/libretro/gambatte-libretro
gearboy- https://github.com/libretro/Gearboy
genesis_plus_gx- https://github.com/libretro/Genesis-Plus-GX
handy- https://github.com/libretro/libretro-handy
mame2003_plus- https://github.com/libretro/mame2003-plus-libretro
mgba- https://github.com/libretro/mgba
mednafen_ngp- https://github.com/libretro/beetle-ngp-libretro
mednafen_pce_fast- https://github.com/libretro/beetle-pce-fast-libretro
mednafen_psx- https://github.com/libretro/beetle-psx-libretro
mednafen_vb- https://github.com/libretro/beetle-vb-libretro
mednafen_wswan- https://github.com/libretro/beetle-wswan-libretro
melonds- https://github.com/libretro/melonDS
o2em- https://github.com/libretro/libretro-o2em
prboom- https://github.com/libretro/libretro-prboom
prosystem- https://github.com/libretro/prosystem-libretro
snes9x- https://github.com/libretro/snes9x
stella2014- https://github.com/libretro/stella2014-libretro
tyrquake- https://github.com/libretro/libretro-tyrquake
vba_next- https://github.com/libretro/vba-next
vecx- https://github.com/libretro/libretro-vecx
virtualjaguar- https://github.com/libretro/virtualjaguar-libretro
yabause- https://github.com/libretro/yabause

Variables and usage

Supported variables

EJS_player- The id of the div you want the libretro canvas to render into.
EJS_gameUrl- The full URL to the game to load.
EJS_core- The libretro core to use.
EJS_biosUrl- Bios URL will be loaded into libretro's system directory, a zip file will be unzipped into this directory.
EJS_onGameStart- Run a custom function after the game is started.

Basic setup

By default the script renders in a canvas element and an unstyled fullscreen button with the class full-button. Feel free to hide the button or style it absolute to where you need it on your page. The user of the game can bring up the libretro menu by pressing F1 on a keyboard or start+select+L+R on a controller. You can define scripts to run after startup by using the onGameStart option, IE to go fullscreen on load:

EJS_onGameStart = function() {
  Module.requestFullscreen(false);
}

The core can be interacted with while running using the Module as seen above to go fullscreen, there are other commands that can be sent also one of the most important being Module._cmd_savefiles() this will force an sram dump of the users save data on supported games/cores. You will want to tie this to an unload or hashchange event on your webpage to ensure the user does not need to go into the menu and manually trigger this action. Some other commands are:

_cmd_load_state()
_cmd_save_state()
_cmd_savefiles()
_cmd_take_screenshot()

Everything is stored in browser storage using an indexDB there is no integrated logic for downloading the files from the browser, but this can easily be built by interacting with the fs directly in the browser. All of the code is open, feel free to modify it to your needs, but do not come here for support, none will be provided. These repositories are simply for development participation only.