mimics Google Search Console's fetch and render, using Nightmare.js

fetch-and-render.js

var argv = process.argv.slice(2);

var urlToTest = argv[0];
var screenshotFilename = argv[1];

if (!screenshotFilename) {
  throw new Error('Invalid screenshot path.')
}

if (!urlToTest) {
  throw new Error('Invalid URL to test.')
}

var PAGE_WIDTH = 1200;
var PAGE_HEIGHT = 10000;
var RENDER_DELAY = 5000;

var pathForScreenshot = require('path').join(__dirname, screenshotFilename);
var Nightmare = require('nightmare');
var nightmare = Nightmare({
  show: false, // this option must be false, otherwise the viewport will not be valid
  waitTimeout: RENDER_DELAY * 2,
  goToTimeout: RENDER_DELAY,
  webPreferences: {
    width: PAGE_WIDTH,
    height: PAGE_HEIGHT
  }
});

function getSEOMeta() {
  var h1s = [];
  document.querySelectorAll('h1').forEach(function (el) {
    h1s.push(el.textContent.trim());
  });

  return {
    title: document.querySelector('head title').textContent,
    h1: h1s
  };
}

function printSEOMeta(result) {
  console.log('title: ' + result.title);
  result.h1.forEach(function (el) {
    console.log('h1: ' + el);
  });
}

nightmare
  .viewport(PAGE_WIDTH, PAGE_HEIGHT)
  .goto(urlToTest)
  .wait(RENDER_DELAY)
  .screenshot(pathForScreenshot)
  .evaluate(getSEOMeta)
  .end()
  .then(printSEOMeta)
  .catch(function (error) {
    console.error('Fetch and render failed: ', error);
  });

usage:

$ node fetch-and-render.js http://www.self.com/story/classic-denim screenshot.png