dispatch event on beat
var BeatEmitter = require('beat-emitter.js');
var BEAT_TIMING_LIST = [1000, 2000, 3000]; // the list of beats as Number Array
var beat = new BeatEmitter(BEAT_TIMING_LIST);
beat.on('beat',function(currentBeat,fired){
});
var audio = document.getElementById('audio-element');
setTimeout(function(){
beat.tickAt(audio.currentTime);
},10);