index.js

const { promises: fs } = require('fs');
const path = require('path');
const ora = require('ora');
const chalk = require('chalk');
const { cosmiconfig } = require('cosmiconfig');
const Prerenderer = require('@prerenderer/prerenderer');
const Puppeteer = require('@prerenderer/renderer-puppeteer');
const htmlnano = require('htmlnano');
const prettyMs = require('pretty-ms');

process.on('unhandledRejection', (reason, promise) => {
  console.log('Unhandled Rejection at:', promise, 'reason:', reason);
  process.exit(1);
});

module.exports = function prerender(bundler) {
  bundler.on('buildEnd', async () => {
    if (process.env.NODE_ENV !== 'production') return;

    console.log('');
    const spinner = ora(chalk.grey('Prerendering')).start();

    let routes = ['/']; // the default route
    let rendererConfig = {};

    const found = await cosmiconfig('prerender').search();
    if (found) {
      const { config } = found;
      if (Array.isArray(config)) {
        routes = config;
      } else {
        if (config.rendererConfig) ({ rendererConfig } = config);
        if (config.routes) ({ routes } = config);
      }
    }

    const { outDir } = bundler.options;

    const prerenderer = new Prerenderer({
      staticDir: outDir,
      renderer: new Puppeteer(rendererConfig),
    });
    await prerenderer.initialize();

    const start = Date.now();

    const renderedRoutes = await prerenderer.renderRoutes(routes);

    await Promise.all(
      renderedRoutes.map(async (route) => {
        const outputDirectory = path.join(outDir, route.route);
        const file = path.resolve(outputDirectory, 'index.html');
        await fs.mkdir(outputDirectory, { recursive: true });
        const { html } = await htmlnano.process(route.html.trim());
        await fs.writeFile(file, html);
      }),
    );

    const end = Date.now();

    spinner.stopAndPersist({
      symbol: '✨ ',
      text: chalk.green(`Prerendered in ${prettyMs(end - start)}.`),
    });

    prerenderer.destroy();
  });
};