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                <div class="wrapper">
  <div class="audio-wrapper">
    <audio src="" controls class="js-audio audio"></audio>

  <div class="toolbar">
    <button class="js-start button button--start">Start</button>
    <button class="js-stop button button--stop">Stop</button>


                $white: #ffffff;
$grey: #E5E5E5;
$grey-dark: #B5B4B9;

$green: #6ABB5C;
$blue: #4FABE4;

body {
  background: $white;

.wrapper {
  padding: 2rem;

.audio-wrapper {
  margin: 0 0 2rem 0;

.audio {
  width: 100%;
  &::-webkit-media-controls-panel {
    background: white;

.toolbar {
  text-align: center

.button {
  transition: all .4s ease-in-out;
  position: inline-block;
  padding: .6rem 1rem;
  background: $white;
  border: 1px solid $grey;
  border-radius: 0;
  outline: none;
  text-transform: uppercase;
  color: $grey-dark;
  &--start:hover {
    background: $green;
    border-color: darken($green, 5);
    color: $white;
  &--stop:hover {
    background: $blue;
    border-color: darken($blue, 5);
    color: $white;



                // We'll save all chunks of audio in this array.
const chunks = [];

// We will set this to our MediaRecorder instance later.
let recorder = null;

// We'll save some html elements here once the page has loaded.
let audioElement = null;
let startButton = null;
let stopButton = null;

 * Save a new chunk of audio.
 * @param  {MediaRecorderEvent} event 
const saveChunkToRecording = (event) => {

 * Save the recording as a data-url.
 * @return {[type]}       [description]
const saveRecording = () => {
    const blob = new Blob(chunks, {
        type: 'audio/mp4; codecs=opus'
    const url = URL.createObjectURL(blob);

    audioElement.setAttribute('src', url);

 * Start recording.
const startRecording = () => {

 * Stop recording.
const stopRecording = () => {

// Wait until everything has loaded
(function() {
    audioElement = document.querySelector('.js-audio');
    startButton = document.querySelector('.js-start');
    stopButton = document.querySelector('.js-stop');
    // We'll get the user's audio input here.
        audio: true // We are only interested in the audio
    }).then(stream => {
        // Create a new MediaRecorder instance, and provide the audio-stream.
        recorder = new MediaRecorder(stream);

        // Set the recorder's eventhandlers
        recorder.ondataavailable = saveChunkToRecording;
        recorder.onstop = saveRecording;

    // Add event listeners to the start and stop button
    startButton.addEventListener('mouseup', startRecording);
    stopButton.addEventListener('mouseup', stopRecording);