server.js

const express   = require('express');
const router    = express.Router();
const fs        = require('fs');
const { exec }  = require('child_process');

const app = express();

// Set ejs template engine
app.set('view engine', 'ejs');
app.use(express.static(__dirname+'/public'));

const assets = 'public/assets';
const videName = 'nature'; // without extension

router.get('/', (req, res) => {

    fs.access(assets+'/images/'+videName+'.jpg', fs.F_OK, (err) => {
        
        if (err) {
            exec(`bin/ffmpeg -i ${assets}/${videName}.mp4 -ss 00:00:04.00 -r 1 -an -vframes 1 -f mjpeg ${assets}/images/${videName}.jpg`, (error, stdout, stderr) => {
                if (error) {
                    return;
                }
    
                res.render('index', {
                    image: `/assets/images/${videName}.jpg`
                });
            });
        }

        if(err === null) {
            res.render('index', {
                image: `/assets/images/${videName}.jpg`
            });
        }
    });
});


router.get('/video', (req, res) => {

    const path = `${assets}/${videName}.mp4`;

    fs.stat(path, (err, stat) => {

        // Handle file not found
        if (err !== null && err.code === 'ENOENT') {
            res.sendStatus(404);
        }

        const fileSize = stat.size
        const range = req.headers.range

        if (range) {

            const parts = range.replace(/bytes=/, "").split("-");

            const start = parseInt(parts[0], 10);
            const end = parts[1] ? parseInt(parts[1], 10) : fileSize-1;
            
            const chunksize = (end-start)+1;
            const file = fs.createReadStream(path, {start, end});
            const head = {
                'Content-Range': `bytes ${start}-${end}/${fileSize}`,
                'Accept-Ranges': 'bytes',
                'Content-Length': chunksize,
                'Content-Type': 'video/mp4',
            }
            
            res.writeHead(206, head);
            file.pipe(res);
        } else {
            const head = {
                'Content-Length': fileSize,
                'Content-Type': 'video/mp4',
            }

            res.writeHead(200, head);
            fs.createReadStream(path).pipe(res);
        }
    });
});

app.use(router);

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
    console.log(`Server listening on port ${PORT}`);
});