JAVASCRIPT

recordrtc

let stream = await navigator.mediaDevices.getUserMedia({video: true, audio: true});
let recorder = new RecordRTCPromisesHandler(stream, {
    type: 'video'
});
recorder.startRecording();

const sleep = m => new Promise(r => setTimeout(r, m));
await sleep(3000);

await recorder.stopRecording();
let blob = await recorder.getBlob();
invokeSaveAsDialog(blob);

recordrtc

navigator.mediaDevices.getUserMedia({
    video: true,
    audio: true
}).then(async function(stream) {
    let recorder = RecordRTC(stream, {
        type: 'video'
    });
    recorder.startRecording();

    const sleep = m => new Promise(r => setTimeout(r, m));
    await sleep(3000);

    recorder.stopRecording(function() {
        let blob = recorder.getBlob();
        invokeSaveAsDialog(blob);
    });
});