Audio is not getting when canvas record

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Javascript

jQuery

Node.js

I am creating an application for screen recorder including audio am using this code for that while am using this code i got screen record working as perfectly,but audio is not getting.i tried this in google chrome.please help me someone

var elementToShare;
var canvasRecorder;
var recordAudio;
var session = {
audio: true,
video: true
};



 document.getElementById('startButton').onclick = function () { navigator.getUserMedia(session, function (mediaStream) {
elementToShare = document.getElementById('temps');
canvasRecorder = RecordRTC(elementToShare, {
    type: 'canvas'
});
canvasRecorder.startRecording();
}, function (error) { log(JSON.stringify(error)); });

document.getElementById('FinishButton').onclick = function () {
canvasRecorder.stopRecording(function (audioVideoWebMURL) {window.open(audioVideoWebMURL);var recordedBlob = canvasRecorder.getBlob();canvasRecorder.getDataURL(function (dataURL) { });
canvasRecorder.save({ audio: true, video: true });  }); };