Customizing your service worker with Create React App is possible, but could be quite difficult and hacky.
Out of the box, CRA uses Workbox GenerateSW webpack plugin to generate service-worker.js file, and you cannot inject any code to it (you could with CRA@1, not any more with since CRA@2)
You have several strategies, I'll start with the simplest one.
Solution 1: provide your own service-worker file
- in
src/index.js enable service worker:
// serviceWorker.unregister()
serviceWorker.register()
in src/serviceWorker.js register your custom file:
// if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
if ('serviceWorker' in navigator) {
// const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
const swUrl = `${process.env.PUBLIC_URL}/custom-service-worker.js`;
You have to change the name cause when running dev server, CRA provides a mock for service-worker.js
in public/ folder, create custom-service-worker.js file. Webpack will copy it as is in the build/ folder
Pros: quick, dirty win
Cons: your custom file is not processed with Webpack (no imports), and you must implement the network caching logic by yourself (assuming you want a PWA) since you're bypassing Workbox plugins
Solution 2: append your code to generated service-worker
There's a module for it: cra-append-sw.
You're in charge to provide the appended code.
Pros: easy setup, takes advantages GenerateSW
Cons: appended code is processed with Babel/Webpack, but not using CRA's config (you could opt-out). Still use GenerateSW which handle network caching for you. Not sure it works when developing locally
Solution 3: use Workbox in custom service-worker file
apply the first 2 steps of solution #1: change src/index.js and src/serviceWorker.js
in src/ folder, create custom-service-worker.js file. It will be processed by Webpack, so you can use ES2016/TypeScript syntax and import modules
/* eslint no-restricted-globals: "off" */
import * as precaching from 'workbox-precaching'
// your own imports
if (self.__precacheManifest) {
precaching.precacheAndRoute(self.__precacheManifest)
}
// your own code
install react-app-rewire:
npm add --save-dev react-app-rewired- in
package.json, in "scripts", replace react-scripts with react-app-rewired
tweak webpack configuration: create config-overrides.js in root folder:
const WebpackBeforeBuildPlugin = require('before-build-webpack')
const WorkboxWebpackPlugin = require('workbox-webpack-plugin')
const path = require('path')
const merge = require('lodash.merge')
const fs = require('fs')
// from https://www.viget.com/articles/run-multiple-webpack-configs-sequentially/
class WaitPlugin extends WebpackBeforeBuildPlugin {
constructor(file, interval = 100, timeout = 60e3) {
super(function(stats, callback) {
const start = Date.now()
function poll() {
if (fs.existsSync(file)) {
callback()
} else if (Date.now() - start > timeout) {
throw Error(`Couldn't access ${file} within ${timeout}s`)
} else {
setTimeout(poll, interval)
}
}
poll()
})
}
}
const swOutputName = 'custom-service-worker.js'
const workerSource = path.resolve(__dirname, 'src', swOutputName)
module.exports = {
webpack: (config, env) => {
// we need 2 webpack configurations:
// 1- for the service worker file.
// it needs to be processed by webpack (to include 3rd party modules), and the output must be a
// plain, single file, not injected in the HTML page
const swConfig = merge({}, config, {
name: 'service worker',
entry: workerSource,
output: {
filename: swOutputName
},
optimization: {
splitChunks: false,
runtimeChunk: false
}
})
delete swConfig.plugins
// 2- for the main application.
// we'll reuse configuration from create-react-app, without a specific Workbox configuration,
// so it could inject workbox-precache module and the computed manifest into the BUILT service-worker.js file.
// this require to WAIT for the first configuration to be finished
if (env === 'production') {
const builtWorkerPath = path.resolve(config.output.path, swOutputName)
config.name = 'main-application'
config.plugins.push(
new WorkboxWebpackPlugin.InjectManifest({
swSrc: builtWorkerPath,
swDest: swOutputName
}),
new WaitPlugin(builtWorkerPath)
)
}
// remove Workbox service-worker.js generator
const removed = config.plugins.findIndex(
({ constructor: { name } }) => name === 'GenerateSW'
)
if (removed !== -1) {
config.plugins.splice(removed, 1)
}
const result = [swConfig, config]
// compatibility hack for CRA's build script to support multiple configurations
// https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/scripts/build.js#L119
result.output = { publicPath: config.output.publicPath }
return result
}
}
Pros: you can use ES2016/TypeScript code in service-worker file. You still benefit from Workbox network caching facilities, with total control on it
Cons: complicated and fragile, because of the multiple configuration hack.
I've used the last solution, cause I needed both caching code from Workbox and some import in my service worker file.
react-app-rewire-workbox may help simplifying the Webpack configuration (the one for main app). To be tested.
