Implementation of Howler.js player code

HowlerImplementation.js

function playTrack(trackNumber, listen) {
    if (track) {
        track.pause();
    }

    if (typeof listen === 'undefined') {
        listen = false;
    }

    var src = base + trackNumber + ".m4a";

    track = new Howl({
        src: src,
        autoplay: false,
        loop: false,
        volume: 1
    });

    console.log("playing " + src);
    track.play();

    track.on("end",
        function() {
            track.off("end");
            if (listen) {
                beginListening();
            }
        });
}