wavesurfer.js + Microphone

var wavesurfer = Object.create(WaveSurfer);

wavesurfer.init({
  container     : '#waveform',
  waveColor     : 'black',
  interact      : false,
  cursorWidth   : 0
});

var microphone = Object.create(WaveSurfer.Microphone);

microphone.init({
    wavesurfer: wavesurfer
});

microphone.on('deviceReady', function(stream) {
    console.log('Device ready!', stream);
});
microphone.on('deviceError', function(code) {
    console.warn('Device error: ' + code);
});

// start the microphone
microphone.start();

// pause rendering
//microphone.togglePlay();

// stop and disconnect microphone
//microphone.stop();