test.js

const puppeteer = require('puppeteer');

var sizes = [
	{
		name: "1080p",
		width: 1920,
		height: 1080,
		isMobile: false
	},
	{
		name: "iPhone X",
		width: 375,
		height: 812,
		isMobile: true
	},
];

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('https://jaxbot.me/');

  for (var i = 0; i < sizes.length; i++) {
	  let size = sizes[i];
	  await page.setViewport(size);
	  await page.screenshot({path: 'example' + size.name + '.png'});
  }

  await browser.close();
})();