virt.js

var startEmulator = function (rom) {

    var engine = Virtjs.create(Virtjs.engine.GameBoy, {

        devices : {
            screen : new Virtjs.screen.WebGL(),
            input : new Virtjs.input.Keyboard({ map : map }),
            timer : new Virtjs.timer.RAFrame(),
            data : new Virtjs.data.LocalStorage()
        },

        skipBios : true

    }).load(rom);

    document.body.appendChild(engine.devices.screen.canvas);

};

( function ( ) {

    var xhr = new XMLHttpRequest();

    xhr.open('GET', 'http://example.org/tetris.gb', true);
    xhr.responseType = 'arraybuffer';

    xhr.addEventListener('load', function () {
        startEmulator(xhr.response); });

    xhr.send(null);

})();