if (navigator.mediaDevices === undefined) {
        navigator.mediaDevices = {};
        navigator.mediaDevices.getUserMedia = function(constraintObj) {
            let getUserMedia = navigator.webkitGetUserMedia || navigator.mozGetUserMedia;
            if (!getUserMedia) {
                return Promise.reject(new Error('getUserMedia is not implemented in this browser'));
            }
            return new Promise(function(resolve, reject) {
                getUserMedia.call(navigator, constraintObj, resolve, reject);
            });
        }
    }
    else{
        navigator.mediaDevices.enumerateDevices()
        .then(devices => {
            devices.forEach(device=>{
                console.log(device.kind.toUpperCase(), device.label);
            })
        })
        .catch(err=>{
            console.log(err.name, err.message);
        })
    }
    navigator.mediaDevices.getUserMedia(constraintObj)
    .then(function(mediaStreamObj) {
        //connect the media stream to the first video element
        let video = document.querySelector('video');
        if ("srcObject" in video) {
            video.srcObject = mediaStreamObj;
        } else {
            video.src = window.URL.createObjectURL(mediaStreamObj);
        }

        video.onloadedmetadata = function(ev) {
            //show in the video element what is being captured by the webcam
            video.play();
        };

        let start = document.getElementById('btnStart');
        let stop = document.getElementById('btnStop');
        let vidSave = document.getElementById('vid2');
        let mediaRecorder = new MediaRecorder(mediaStreamObj);
        let chunks = [];

        start.addEventListener('click', (ev)=>{
            mediaRecorder.start();
            console.log(mediaRecorder.state);
        })
        stop.addEventListener('click', (ev)=>{
            mediaRecorder.stop();
            console.log(mediaRecorder.state);
        });
        mediaRecorder.ondataavailable = function(ev) {
            chunks.push(ev.data);
        }
        mediaRecorder.onstop = (ev)=>{
            let blob = new Blob(chunks, { 'type' : 'video/mp4;' });
            chunks = [];
            let videoURL = window.URL.createObjectURL(blob);
            vidSave.src = videoURL;
        }
    })
    .catch(function(err) {
        console.log(err.name, err.message);
    });