Shuvo

Posted on Oct 21, 2021

Lets create a screen recorder with JS

#javascript #webdev #tutorial #beginners

OBS studio is cool but lets create our very own screen recorder using JavaScript.
And guess what? Its not limited to just recording the browser screen. Yes, you've read that right. Although JavaScript runs on browser, we can use JS to record not only the active tab but any tab or entire screen. So lets get started.
First thing we'd need is a HTML file, in that we will have a record button and a video element where we can play the recorded video.



<!DOCTYPE html>
<html>
  <head>
    <title>Parcel Sandbox</title>
    <meta charset="UTF-8" />
  </head>
  <body>
    <video class="video" width="600px" controls></video>
    <button class="record-btn">record</button>

    <script src="./index.js"></script>
  </body>
</html>

And we'd also need a JS file so lets create the index.js also



let btn = document.querySelector(".record-btn");

btn.addEventListener("click", function () {
  console.log("hello");
});

So now if we open it the browser and click on the button we should see hello in console.

Alright now instead of console.log lets get the stream of users display



let btn = document.querySelector(".record-btn");

btn.addEventListener("click", async function () {
  let stream = await navigator.mediaDevices.getDisplayMedia({
    video: true
  });
});

So now if you click on the button you'll see this popup.

Now you might think we are done select a window or screen and click share and it should start recording. But its a bit more complicated than that. We have to record the video our self. We are going to use MediaRecorder to record our video.



let btn = document.querySelector(".record-btn")

btn.addEventListener("click", async function () {
  let stream = await navigator.mediaDevices.getDisplayMedia({
    video: true
  })

  //needed for better browser support
  const mime = MediaRecorder.isTypeSupported("video/webm; codecs=vp9") 
             ? "video/webm; codecs=vp9" 
             : "video/webm"
    let mediaRecorder = new MediaRecorder(stream, {
        mimeType: mime
    })

    //we have to start the recorder manually
    mediaRecorder.start()
})

So as our screen get recorded mediaRecorder will give us data in chunks we need to store those data in a variable.



let btn = document.querySelector(".record-btn")

btn.addEventListener("click", async function () {
  let stream = await navigator.mediaDevices.getDisplayMedia({
    video: true
  })

  //needed for better browser support
  const mime = MediaRecorder.isTypeSupported("video/webm; codecs=vp9") 
             ? "video/webm; codecs=vp9" 
             : "video/webm"
    let mediaRecorder = new MediaRecorder(stream, {
        mimeType: mime
    })

    let chunks = []
    mediaRecorder.addEventListener('dataavailable', function(e) {
        chunks.push(e.data)
    })

    //we have to start the recorder manually
    mediaRecorder.start()
})

And now when we click on the stop sharing button we want the recorded video to be played in our video element so lets do that.



let btn = document.querySelector(".record-btn")

btn.addEventListener("click", async function () {
  let stream = await navigator.mediaDevices.getDisplayMedia({
    video: true
  })

  //needed for better browser support
  const mime = MediaRecorder.isTypeSupported("video/webm; codecs=vp9") 
             ? "video/webm; codecs=vp9" 
             : "video/webm"
    let mediaRecorder = new MediaRecorder(stream, {
        mimeType: mime
    })

    let chunks = []
    mediaRecorder.addEventListener('dataavailable', function(e) {
        chunks.push(e.data)
    })

    mediaRecorder.addEventListener('stop', function(){
      let blob = new Blob(chunks, {
          type: chunks[0].type
      })

      let video = document.querySelector(".video")
      video.src = URL.createObjectURL(blob)
  })

    //we have to start the recorder manually
    mediaRecorder.start()
})

Now as a finishing touch lets automatically download the recorded video.



let btn = document.querySelector(".record-btn")

btn.addEventListener("click", async function () {
  let stream = await navigator.mediaDevices.getDisplayMedia({
    video: true
  })

  //needed for better browser support
  const mime = MediaRecorder.isTypeSupported("video/webm; codecs=vp9") 
             ? "video/webm; codecs=vp9" 
             : "video/webm"
    let mediaRecorder = new MediaRecorder(stream, {
        mimeType: mime
    })

    let chunks = []
    mediaRecorder.addEventListener('dataavailable', function(e) {
        chunks.push(e.data)
    })

    mediaRecorder.addEventListener('stop', function(){
      let blob = new Blob(chunks, {
          type: chunks[0].type
      })
      let url = URL.createObjectURL(blob)

      let video = document.querySelector("video")
      video.src = url

      let a = document.createElement('a')
      a.href = url
      a.download = 'video.webm'
      a.click()
  })

    //we have to start the recorder manually
    mediaRecorder.start()
})

And there now we have a fully functional screen recorder app.

Make sure to read my other articles.

Python + JavaScript = 🔥🔥🔥

Shuvo ・ Oct 21 '21

#javascript #node #python #programming

Shuvo

Frontend Developer and YouTuber. Channel link: https://www.youtube.com/c/AngleBrace

Top comments (49)

Branko Stancevic • Oct 23 '21 • Edited

Great article! Keep it up! However, I have question...

Why you need to create chunks when e.data in dataavailable is already a blob?

Isn't that part kinda unnecessary?

Couldn't we just use it like this?

  let blob = null;

  mediaRecorder.addEventListener('dataavailable', (e) => {
    blob = e.data;
  })

Shuvo • Oct 23 '21

as you keep recording the dataavailable event will run multiple time. So basically instead you giving you the entire video once recording is done it will give you data in small parts as the video is being recorded.

Branko Stancevic • Oct 23 '21

Ok cool! Thank you

Amran AL Ketara • Oct 21 '21

YOU ARE AWESOME MAN!!
Do you have a YouTube channel, blog or something like that?

Shuvo • Oct 21 '21

Many many Thank.
Yes, I have a YouTube channel.
But I am introvert so I struggle to talk which is why my videos are not that good. But I'm trying to improve
youtu.be/mD_QQvJYQAI

Usman Khalil • Oct 24 '21

Very clear explanation. Loved it

Shuvo • Oct 24 '21

Many many Thanks

Usman Khalil • Oct 24 '21

The minute I saw the tutorial, the next thing I knew was that I'm gonna make this thing my self. Created in React and deployed. Thank you once again.

Shuvo • Oct 24 '21

Damn thats really great.
If you want something way more challenging you can try this

Usman Khalil • Oct 24 '21

Damn. You just earned a follower and my respect. Keep those challenges coming coach.

Shuvo • Oct 24 '21

Thanks a lot.
I also followed you back.

Jose Antonio Felix • Oct 22 '21

It's pretty cool !!! thank you man

Shuvo • Oct 23 '21

You're most welcome

Cooper4111 • Aug 23 '22 • Edited

TL;DR: your solution generates broken files for chrome.

There's an issue with Chrome, that leads to losing metadata on video files created using MediaRecorder. The file is playable, yet, it has no duration so you can't scroll it and it's always 00:00 / 00:00. You've added
let video = document.querySelector("video") video.src = url
Which is meaningless, unless you're trying to implement this workaround. But it requires changing the currentTime and doesn't actually work for saved file, only for <video> tag in document.

I'm not being toxic about your topic, just struggling myself to solve this. Any ideas are welcome.

pranavps020 • Mar 7 '22

Great Article mate , getDisplayMedia isn't supported in android& ios. Is thre any work around ?. All I'm looking for is to record a webpage as a video don't have to record out side browser like getDisplayMedia.

andiduferense • Feb 23 '22 • Edited

Why bother when you can use the usual programs like this and not bother. I just like such programs for their simplicity and convenience. Even a child can relax with them.