Can I create a simple program in Javascript which captures the screen recording and saves the recorded file?
Yes, you can create a simple JavaScript program to capture the screen and save the recording as a file. This can be done using the MediaDevices API to capture the screen and the MediaRecorder API to record the stream. Here’s a step-by-step guide to creating a basic screen recording program.
Step-by-Step Code Example
This example will prompt the user to select a screen or application window to record, record the stream, and save it as a .webm file.
html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Screen Recorder</title>
</head>
<body>
<h1>Screen Recorder</h1>
<button id="startBtn">Start Recording</button>
<button id="stopBtn" disabled>Stop Recording</button>
<video id="preview" controls autoplay></video>
<script>
let mediaRecorder;
let recordedChunks = [];
const startBtn = document.getElementById('startBtn');
const stopBtn = document.getElementById('stopBtn');
const preview = document.getElementById('preview');
startBtn.addEventListener('click', async () => {
// Request screen capture
const stream = await navigator.mediaDevices.getDisplayMedia({
video: true,
audio: true
});
// Preview the screen capture in the video element
preview.srcObject = stream;
// Initialize MediaRecorder for the stream
mediaRecorder = new MediaRecorder(stream, {
mimeType: 'video/webm; codecs=vp9'
});
// Store recorded chunks when data is available
mediaRecorder.ondataavailable = (event) => {
if (event.data.size > 0) {
recordedChunks.push(event.data);
}
};
// Handle stop event to save the recorded file
mediaRecorder.onstop = () => {
const blob = new Blob(recordedChunks, { type: 'video/webm' });
const url = URL.createObjectURL(blob);
// Download the recorded video
const a = document.createElement('a');
a.href = url;
a.download = 'recorded_screen.webm';
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
// Reset chunks for the next recording
recordedChunks = [];
};
// Start recording
mediaRecorder.start();
startBtn.disabled = true;
stopBtn.disabled = false;
});
stopBtn.addEventListener('click', () => {
// Stop recording and screen stream
mediaRecorder.stop();
preview.srcObject.getTracks().forEach(track => track.stop());
startBtn.disabled = false;
stopBtn.disabled = true;
});
</script>
</body>
</html>
Explanation of the Code
HTML Structure:
We have two buttons (Start Recording and Stop Recording) and a <video> element to preview the screen recording.
JavaScript Logic:
Button Event Listeners: When the "Start Recording" button is clicked, the program:
Requests the user’s permission to capture the screen using navigator.mediaDevices.getDisplayMedia().
Creates a MediaRecorder instance to record the screen.
Sets up handlers for ondataavailable (to capture recording data in chunks) and onstop (to save the recorded video file).
Saving the Video File:
When recording stops, the captured chunks are assembled into a Blob, which is then turned into a downloadable .webm file.
Stop Recording: The "Stop Recording" button stops the MediaRecorder and terminates the screen capture stream.
Key Points to Remember
MIME Type: This example uses video/webm with VP9 codec, which is widely supported for web-based recording.
Browser Compatibility: This should work in most modern browsers that support MediaDevices and MediaRecorder APIs (e.g., Chrome, Edge, and Firefox).
Audio Capture: This example enables audio capture if available (selected in screen sharing). If you want to omit audio, set audio: false in getDisplayMedia().
This code provides a simple setup for capturing, previewing, and saving screen recordings directly from a web page using JavaScript.
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