This page explains how to use the workbox-build
Node module to generate a
complete service worker with precaching and runtime caching.
Install workbox-build
Start by installing workbox-build
from npm.
npm install workbox-build --save-dev
Call generateSW()
To generate a service worker, you need to add workboxBuild.generateSW()
to your build process or Node script:
const workboxBuild = require('workbox-build');
// NOTE: This should be run *AFTER* all your assets are built
const buildSW = () => {
// This will return a Promise
return workboxBuild.generateSW({
globDirectory: 'build',
globPatterns: [
'**/*.{html,json,js,css}',
],
swDest: 'build/sw.js',
});
};
This command will output a service worker to build/sw.js
which
will precache all the files in the build/
directory that match
any of the globPatterns
defined.
In your web page, you can register this service worker by adding:
<script> // Check that service workers are supported if ('serviceWorker' in navigator) { // Use the window load event to keep the page load performant window.addEventListener('load', () => { navigator.serviceWorker.register('/service-worker.js'); }); } </script>
Adding Runtime Caching
There may be files that you don't want to precache but will be used by your web app that you'd like to cache at runtime. Images are a great example.
Instead of precaching all images for your site, which will take up a lot of space in the cache, you can cache them as they are used and limit the number of images cached.
Runtime caching can be achieved by adding the runtimeCaching
configuration
to the options passed into generateSW()
. runtimeCaching
expects an
array of objects that describe the runtime caching rules you want.
In the example below, we'll demonstrate how to cache images and limit that cache to a maximum of 10 images.
const workboxBuild = require('workbox-build');
// NOTE: This should be run *AFTER* all your assets are built
const buildSW = () => {
// This will return a Promise
return workboxBuild.generateSW({
globDirectory: 'build',
globPatterns: [
'**/*.{html,json,js,css}',
],
swDest: 'build/sw.js',
// Define runtime caching rules.
runtimeCaching: [{
// Match any request that ends with .png, .jpg, .jpeg or .svg.
urlPattern: /\.(?:png|jpg|jpeg|svg)$/,
// Apply a cache-first strategy.
handler: 'CacheFirst',
options: {
// Use a custom cache name.
cacheName: 'images',
// Only cache 10 images.
expiration: {
maxEntries: 10,
},
},
}],
});
};
buildSW();
The full set of available options can be found on the
workbox-build
module page.
Using with Gulp
Using workbox-build
with your Gulp process is simply a case of using the same
code as above as a Gulp task.
const gulp = require('gulp');
const workboxBuild = require('workbox-build');
gulp.task('service-worker', () => {
return workboxBuild.generateSW({
globDirectory: 'build',
globPatterns: [
'**/*.{html,json,js,css}',
],
swDest: 'build/sw.js',
});
});
After this you can simply run the task via gulp service-worker
or add it
to the end of another Gulp task.