Chromium page per handler with Puppeteer and Express.js

index.js

const puppeteer = require('puppeteer');
const express = require('express');
const asyncHandler = require('express-async-handler');

(async () => {
  // initialise Express.js framework
  const app = express();
  
  // start chromium browser
  let browser = await puppeteer.launch({headless: true});
  
  // browser restart
  browser.addListener('disconnected', async () => {
    browser = await puppeteer.launch({headless: true});
  });
  
  // empty page for preventing browser closing
  await browser.newPage();

  // routes
  app.get('/', asyncHandler(async (request, response) => {
    console.log((await browser.pages()).length);
    const url = request.query.url;
    // TODO: validation

    const page = await browser.newPage();
    
    await page.goto(url);
    const buffer = await page.pdf({format: 'A4'});
    await page.close();
    
    response.type('pdf');
    response.send(buffer);
  }));

  app.listen(3000, function () {
    console.log('Example app listening on port 3000!');
  });
})();