Service Worker Development Cookbook

By Sean Amarasinghe

About This Book

• Get straight into the action with step-by-step recipes that show you how to put Service Workers to work
• Find out what Service Workers can do for your app, then do it!
• Get the first in-depth look at this important new feature for web developers

Who This Book Is For

Web developers, mobile application developers, and software engineers with any level of knowledge can use this book. You should be familiar with JavaScript and HTML.

• Language: English
• Publisher: Packt Publishing
• Release date: Sep 1, 2016
• ISBN: 9781786469526

Book preview

Table of Contents

Service Worker Development Cookbook

Credits

About the Author

About the Reviewer

www.PacktPub.com

eBooks, discount offers, and more

Why subscribe?

Preface

What this book covers

What you need for this book

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Learning Service Worker Basics

Introduction

Service workers

Promises

Promise.resolve(value)

Promise.reject(reason)

Setting up service workers

Getting ready

How to do it...

Chrome

Firefox

Setting up SSL for Windows

Getting ready

How to do it...

Setting up SSL for Mac

Getting ready

How to do it...

Setting up GitHub pages for SSL

Getting ready

How to do it...

Registering a service worker

Getting ready

How to do it...

How it works...

There's more...

Known issues

The ERR_FILE_EXISTS error message

Stale console messages

Registering a service worker in detail

Getting ready

How to do it...

How it works...

There's more...

Install

Activate

Fetch

Terminate

See also

Debugging

Getting ready

How to do it...

There's more...

Providing a stale version on error

Getting ready

How to do it...

How it works...

There's more...

Creating mock responses

Getting ready

How to do it...

How it works...

Handling request timeouts

Getting ready

How to do it...

How it works...

There's more...

2. Working with Resource Files

Introduction

Displaying a custom offline page

Getting ready

How to do it...

How it works...

There's more...

See also

Loading images offline

Getting ready

How to do it...

How it works...

There's more...

Handling responsive images

The srcset attribute

Device-pixel ratio

The sizes attribute

The picture element

See also

Loading CSS offline

Getting ready

How to do it...

How it works...

Loading fonts offline

Getting ready

How to do it...

How it works...

There's more...

See also

Implementing multiple fetch handlers

Getting ready

How to do it...

How it works...

There's more...

See also

Fetching remote resources

Getting ready

How to do it...

How it works...

There's more...

No credentials by default

Non-CORS fail by default

See also

3. Accessing Offline Content

Introduction

Caching critical resources for offline use

Getting ready

How to do it...

How it works...

See also

Showing cached content first

Getting ready

How to do it...

How it works...

Implementing a cache and network race

Getting ready

How to do it...

How it works...

Using window.caches

Getting ready

How to do it...

How it works...

Implementing stale-while-revalidate

Getting ready

How to do it...

How it works...

4. Accessing Offline Content with Advanced Techniques

Introduction

Templating

Getting ready

How to do it...

How it works...

See also

Implementing read-through caching

Getting ready

How to do it...

How it works...

Allowing offline Google Analytics

Getting ready

How to do it...

How it works...

See also

Allowing offline user interaction

Getting ready

How to do it...

How it works...

Implementing selective caching

Getting ready

How to do it...

How it works...

See also

5. Reaching Beyond the Offline Cache

Introduction

Getting network responses offline

Getting ready

How to do it...

How it works...

Caching content from ZIP

Getting ready

How to do it...

How it works...

Selecting the best content provider (load balancer)

Getting ready

How to do it...

How it works...

Redirecting a request

Getting ready

How to do it...

How it works...

Setting request headers

Getting ready

How to do it...

How it works...

Making a service worker act like a remote server

Getting ready

How to do it...

How it works...

Making a service worker act as a dependency injector

Getting ready

How to do it...

How it works...

Forcing immediate control

Getting ready

How to do it...

How it works...

Implementing fallback responses

Getting ready

How to do it...

How it works...

Deferring offline requests

Getting ready

How to do it...

How it works...

See also

6. Working with Advanced Libraries

Introduction

Working with global APIs

Getting ready

How to do it...

How it works...

Cache

caches

fetch

getAll

Implementing a circuit breaker

Getting ready

How to do it...

How it works...

Implementing a dead letter queue

Getting ready

How to do it...

How it works...

Logging API analytics

Getting ready

How to do it...

How it works...

Working with Google Analytics

Getting ready

How to do it...

How it works...

See also

7. Fetching Resources

Introduction

Fetching remote resources

Getting ready

How to do it...

How it works...

Fetching with FetchEvent

Getting ready

How to do it...

How it works...

Cache.addAll()

ExtendableEvent.waitUntil()

FetchEvent.respondWith()

Fetching a JSON file during service worker installation

Getting ready

How to do it...

How it works...

Proxying

Getting ready

How to do it...

How it works...

Prefetching

Getting ready

How to do it...

How it works...

8. Experimenting with Web Push

Introduction

Implementing a simple push notification

Getting ready

How to do it...

How it works...

Showing rich notifications

Getting ready

How to do it...

How it works...

Using the notification tag

Getting ready

How to do it...

How it works...

Implementing push clients

Getting ready

How to do it...

How it works...

Subscribing to push notifications

Getting ready

How to do it...

How it works...

Managing push notification quotas

Getting ready

How to do it...

How it works...

9. Looking at General Usage

Introduction

Taking immediate control of the page

Getting ready

How to do it...

How it works...

Working with slow responses

Getting ready

How to do it...

How it works...

Relaying messages

Getting ready

How to do it...

How it works...

Using a service worker as a proxy middleware

Getting ready

How to do it...

How it works...

Using a service worker with a live flowchart

Getting ready

How to do it...

How it works...

10. Improving Performance

Introduction

Performing network requests from a cache

Getting ready

How to do it...

How it works...

See also

Performing network requests from a network

Getting ready

How to do it...

How it works...

See also

Testing waitUntil

Getting ready

How to do it...

How it works...

Implementing background sync

Getting ready

How to do it...

How it works...

Sending forward requests

Getting ready

How to do it...

How it works...

Avoiding model fetching and render times

Getting ready

How to do it...

How it works...

Index

Service Worker Development Cookbook

---

Service Worker Development Cookbook

Copyright © 2016 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: August 2016

Production reference: 1260816

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-78646-529-0

www.packtpub.com

Credits

Author

Sean Amarasinghe

Reviewer

Daijiro Wachi

Commissioning Editor

David Barnes

Acquisition Editor

Nitin Dasan

Content Development Editor

Mehvash Fatima

Technical Editor

Siddhi Rane

Copy Editors

Safis Editing

Tom Jacob

Project Coordinator

Kinjal Bari

Proofreader

Safis Editing

Indexer

Hemangini Bari

Graphics

Kirk D'Penha

Production Coordinator

Shantanu N. Zagade

Cover Work

Shantanu N. Zagade

About the Author

Sean Amarasinghe is a software developer from Melbourne, Australia. He is a developer, designer, photographer, and also a blogger. He blogs about development, design, technology, and photography. He is passionate about offline apps and what they bring to the user. He has firsthand experience of how well offline apps work. He has written a couple of blog posts about offline cache manifests, as well as service workers.

About the Reviewer

Daijiro Wachi is a JavaScript developer from Tokyo, Japan. He is passionate about open web and some of open source projects/communities related to JavaScript on a daily basis. He has gained the highest award in Service Worker Hackathon 2015 held by Google Japan.

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Preface

The service worker feature of the browser will enable you to build highly available and performant native web applications that seamlessly integrate with third-party APIs. Whether you want to create an offline web app or a proxy, this book will show you how to do it.

What this book covers

Chapter 1, Learning Service Worker Basics, covers setting up the service worker in your environment, and how to get up and running using service worker development. This chapter includes registering a service worker and debugging.

Chapter 2, Working with Resource Files, provides several recipes on how to handle resource files with the service worker, including loading CSS and fonts.

Chapter 3, Accessing Offline Content, takes a look at how to cache resources and serve content offline.

Chapter 4, Accessing Offline Content with Advanced Techniques, explores advanced techniques, including templating and Google Analytics, when working with offline content.

Chapter 5, Reaching Beyond the Offline Cache, provides recipes beyond the offline cache and explores topics ranging from getting network responses offline to how to use the service worker as a load balancer.

Chapter 6, Working with Advanced Libraries, talks about Google Analytics, circuit breakers, and dead letter queues.

Chapter 7, Fetching Resources, covers various techniques on fetching resources from different sources.

Chapter 8, Experimenting with Web Push, talks about different ways of implementing push notifications.

Chapter 9, Looking at General Usage, provides various recipes on general usages of the service worker from slow responses to a live flowchart.

Chapter 10, Improving Performance, talks about how to optimize your service worker application to perform efficiently and in a performant manner.

What you need for this book

This book was written using a Mac with Google Chrome as the browser, running Node.js. However, Node.js can be run on a Windows or Linux machine as well, along with Google Chrome.

All the software used in this book is free and open source. You will definitely need to be running Node.js and Google Chrome for most of the recipes.

Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: The skipWaiting() method is used inside the active event handler, which in turn uses Clients.claim().

A block of code is set as follows:

self.oninstall = function(event) {

  event.waitUntil(

    fetch(zipURL)

      .then(function(res) {

        return res.arrayBuffer();

      })

      .then(getZipFileReader)

      .then(cacheFileContents)

      .then(self.skipWaiting.bind(self))

  );

};

Any command-line input or output is written as follows:

$ git add –all $ git commit -m initial commit $ git push -u origin master

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes, for example, appear in the text like this: Finally, in the sidebar on the left-hand side, select Credentials.

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Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.

Downloading the example code

You can download the example code files for this book from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

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Questions

If you have a problem with any aspect of this book, you can contact us at <[e-mail]>, and we will do our best to address the problem.

Chapter 1. Learning Service Worker Basics

In this chapter, we will cover the following topics:

Setting up service workers

Setting up SSL for Windows

Setting up SSL for Mac

Setting up GitHub pages for SSL

Registering a service worker

Registering a service worker in detail

Debugging

Providing stale version on error

Creating mock responses

Handling request timeouts

Introduction

If you travel a bit, chances are you have probably found yourself stuck with zero network connectivity way too often. This is frustrating, especially if you just wanted to continue reading some news articles, blog posts, or you wanted to get some work done.

Unfortunately, with your browser, attempting to make requests for something from the network while being offline doesn't quite work out so well.

Even though on planes, the subway, in hotels, and at conferences, Wi-Fi may provide you with opportunities to restore your connection, in general you will have to wait for the network to return online in order to request the pages you want to view.

Previous attempts to solve this issue include AppCache. It seems to work, to some extent, but the issue with AppCache is that it makes a lot of assumptions about user interactions. When those assumptions are not met, the application will fail to function as expected. It is also designed to work well with single page apps, not the traditional multi-page websites.

Also, one of the most challenging problems with providing a seamless user experience with web apps is making them functional while offline. This is an important issue to resolve, given that most users today access web apps on the move. Enter service workers, a script running in the background of our browser.

Being able to use a web app, regardless of the connectivity, means users can operate uninterrupted when they are on board a plane, the subway, or in places where connectivity is limited or not available. This technology will help boost client productivity and will increase the availability of the application.

With service workers, we are able to pre-cache some assets of a website. What we are referencing as assets are JavaScript files, CSS files, images, and some fonts. This will help us to speed up the loading time, instead of having to fetch information from the web servers every time we visit the same website. And of course, most importantly, those assets will be available for us when we are offline.

Service workers

A service worker is a script that stands between your browser and the network, giving you, among