Generate service worker file

sample-sw.js

importScripts('/js/workbox-sw.js');
workbox.setConfig({
  debug : true
});
workbox.core.setLogLevel(workbox.core.LOG_LEVELS.debug);
workbox.skipWaiting();
workbox.clientsClaim();
workbox.core.setCacheNameDetails({
  "prefix" : "nodepwa",
  "suffix" : "web",
  "precache" : "install-time",
  "runtime" : "run-time"
});
const fileManifest = [
  {
    "url" : "/css/app.css",
    "revision" : "c5be93286dfb80f7b59a4a58191ab6c8"
  }, {
    "url" : "/js/vendor/jquery-3.2.1.slim.min.js",
    "revision" : "d7a8202ab8c3362b7945b133f5ac5d6a"
  }
];
workbox.precaching.precacheAndRoute(fileManifest);

sw-build.js

const crypto = require('crypto'), fs = require('fs')

const fileHash = (filename, url = '', algorithm = 'md5') => {
  return new Promise((resolve, reject) => {
    // Algorithm depends on availability of OpenSSL on platform
    // Another algorithms: 'sha1', 'md5', 'sha256', 'sha512' ...
    let shasum = crypto.createHash(algorithm);
    try {
      let s = fs.ReadStream(filename)
      s.on('data', (data) => {
        shasum.update(data)
      })
      s.on('end', () => {
        const hash = shasum.digest('hex')
        return  resolve({ url, revision: hash });
      })
    } catch (error) {
      return reject('calc fail');
    }
  });
}

const swConfig = (strings, ...values) => {
  const _fileManifest = values[0] || [];
  const _wboxPath = values[1] || '/js/workbox-sw.js';
  const debugMode = values[2] || false;
  const cacheNames = values[3] || {};
  return (`importScripts('${_wboxPath}');
    workbox.setConfig({ debug: ${debugMode} });
    workbox.core.setLogLevel(workbox.core.LOG_LEVELS.debug);
    workbox.skipWaiting();
    workbox.clientsClaim();
    workbox.core.setCacheNameDetails(${cacheNames});
    const fileManifest = ${_fileManifest};
    workbox.precaching.precacheAndRoute(fileManifest);`).replace(/  /gm, '');
};

const displayServiceWorker = (strings, ...values) => {
  const pathToSW = values[0] || '/sw.js';
  return (`<script>
if ('serviceWorker' in navigator) {
  window.addEventListener('load', function() {
    navigator.serviceWorker.register('${pathToSW}').then(function(registration) {
      console.log('ServiceWorker registration successful with scope: ', registration.scope);
    }, function(err) {
      console.log('ServiceWorker registration failed: ', err);
    });
  });
}
</script>
`)
};

const config = require(__dirname + '/sw-config.js');

const tasks = config.fileManifest.map((item) => {
  return fileHash(item.path, item.url)
});

tasks.reduce((promiseChain, currentTask) => {
    return promiseChain.then(chainResults =>
    currentTask.then(currentResult =>
        [ ...chainResults, currentResult ]
    )
);
}, Promise.resolve([])).then(arrayOfResults => {
  const manifestData = JSON.stringify(arrayOfResults);
  const serviceWorkerContent = swConfig`File manifest data: ${manifestData}; path to workbox file ${config.pathToWorkbox}; debug mode: ${true}; cache names: ${JSON.stringify(config.cacheNames)}`;
  fs.writeFileSync(config.swOutputFile, serviceWorkerContent);
  console.log('Add following script to your HTML:\n---');
  console.log(displayServiceWorker`Path to sw.js ${'/sw.js'}`)
});

// https://decembersoft.com/posts/promises-in-serial-with-array-reduce/
// https://stackoverflow.com/questions/20100245/how-can-i-execute-array-of-promises-in-sequential-order

sw-config.js

module.exports = {
    fileManifest: [
      {
        path: __dirname + '/public/css/app.css',
        url: '/css/app.css'
      },
      {
        path: __dirname + '/public/js/vendor/jquery-3.2.1.slim.min.js',
        url: '/js/vendor/jquery-3.2.1.slim.min.js'
      }
    ],
    
    debugMode: true,
    
    logLevel: 'debug',
    
    pathToWorkbox: '/js/workbox-sw.js',
    
    swOutputFile: __dirname + '/public/sw.js',
    
    cacheNames: {
      prefix: 'nodepwa',
      suffix: 'web',
      precache: 'install-time',
      runtime: 'run-time'
    }
};