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prerender.js
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prerender.js
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const puppeteer = require('puppeteer');
const express = require('express');
const { join, dirname } = require('path');
const { readFile, exists, writeFile, mkdir } = require('mz/fs')
const { uniq, difference } = require('lodash');
// Defining some configuration
const PORT = 4000;
const HOST = `http://localhost:${PORT}`;
let PAGES = [''];
let RENDERED_PAGES = [];
async function main() {
// Starting an Express.js server to serve the static files while puppeter prerender the pages
const app = express();
// Getting the html content from the index.html file
const index = (await readFile(join(process.cwd(), 'dist', 'index.html'))).toString();
// Serving the static files.
app.get('*.*', express.static(join(process.cwd(), 'dist')));
// Serving index.html, when a puppeters request the index page
app.get('*', (req, res) => res.send(index));
// Starting the express server
const server = await (new Promise((resolve, reject) => {
const s = app.listen(PORT, e => e ? reject(e) : resolve(s));
}));
console.log(`Started server ${HOST}!`);
// Launching Puppeteer
const browser = await puppeteer.launch();
console.log(`Started browser!`);
// Creating a new Tap/Page
const page = await browser.newPage();
do {
const p = PAGES[0];
// Requesting the first page in PAGES array
await page.goto(`${HOST}/${p}`);
// Getting the html content after the Chromium finish rendering.
const result = await page.evaluate(() => document.documentElement.outerHTML);
// Defining the html file name that will be created
const file = join(process.cwd(), 'dist', (p || 'index') + '.html');
const dir = dirname(file);
// Test if the directory exist, if not create the directory
if (!(await exists(dir)))
await mkdir(dir);
// Write the rendered html file
await writeFile(file, result);
console.log(`Writed ${file}`);
// Add this page to the RENDERED PAGES array
RENDERED_PAGES = [...RENDERED_PAGES, p];
// Set PAGES with the pages that still need to be rendered
PAGES = difference(
uniq(PAGES.concat(result.match(/href="\/[\/\w\d\-]*"/g).map(s => s.match(/\/([\/\w\d\-]*)/)[1]))),
RENDERED_PAGES
);
} while (PAGES.length > 0);
// Closes Chromium and finishes the express server.
browser.close();
server.close();
}
// Run the main asyn function
main()
.then(() => console.log('All right!'))
.catch(err => {
console.error('Err', err);
process.exit(1);
});