Screenshot grabber that uses headless chrome (only works on mac)

headless-screenshots.js

/** Pre requisites
1) Make an Alias to Chrome
  alias chrome="/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome"
  alias chrome-canary="/Applications/Google\ Chrome\ Canary.app/Contents/MacOS/Google\ Chrome\ Canary"
  
2) Make Sure yarn is installed (it caches packages so you don't have to download them again)
    `npm i yarn`

3) Use yarn to install dependencies:
  `yarn add lighthouse`
  `yarn add chrome-remote-interface`

 * USAGE:
 * `node headless-screenshot.js -w 1024 -h 768 --url=http://google.com`
 */

/* Dependencies */
const chromeLauncher = require('lighthouse/chrome-launcher/chrome-launcher');
const CDP = require('chrome-remote-interface');
const fs = require('fs');

/** ARGUMENTS AND CONFIGUIRATION
 * expects arguments to be
 * -w int (width)
 * -h int (height)
 * -p int (port)
 * --url string (url)
 */

const argv = require('minimist')(process.argv.slice(2));
const windowWidth = argv.w ? argv.w : 1024;
const windowHeight = argv.h ? argv.h : 1024;
const launchConfig = {
    chromeFlags: [
        `--window-size=${windowWidth},${windowHeight}`,
        '--disable-gpu',
        '--headless'
    ]
}

/** saveScreenshot
 * 
 * @param {String} imageData base64 string
 */
function saveScreenshot(imageData) {
    const filename = `${argv.url.replace('http://','').replace(/\//g,'_')}.png`;

    fs.writeFile(
        filename,
        imageData.data, {encoding:'base64'},
        (err)=>{
            console.warn('error', err);
        }
    );
}

/**
 * Launches a debugging instance of Chrome.
 *     False launches a full version of Chrome.
 * @return {Promise<ChromeLauncher>}
 */
async function launchChrome(headless = true) {
  return await chromeLauncher.launch(launchConfig);
}


 (async function() {
     const chrome = await launchChrome();
     const protocol = await CDP({port: chrome.port});
     const {Page, Runtime} = protocol;

     await Promise.all([Page.enable(), Runtime.enable()]);

     Page.navigate({url: argv.url});

     Page.loadEventFired(async () => {
        const titleJS = "document.querySelector('title').textContent";
        const pageTitle = await Runtime.evaluate({expression: titleJS});
        const screenshot = await Page.captureScreenshot();

        console.log(`title of page: ${pageTitle.result.value}`);

        Promise.resolve(screenshot).then((imageData)=>{
            saveScreenshot(imageData);
        });

        protocol.close()
        chrome.kill();
     });
 })()