Book Image

Learn ECMAScript - Second Edition

By : MEHUL MOHAN, Narayan Prusty
Book Image

Learn ECMAScript - Second Edition

By: MEHUL MOHAN, Narayan Prusty

Overview of this book

Learn ECMAScript explores implementation of the latest ECMAScript features to add to your developer toolbox, helping you to progress to an advanced level. Learn to add 1 to a variable andsafely access shared memory data within multiple threads to avoid race conditions. You’ll start the book by building on your existing knowledge of JavaScript, covering performing arithmetic operations, using arrow functions and dealing with closures. Next, you will grasp the most commonly used ECMAScript skills such as reflection, proxies, and classes. Furthermore, you’ll learn modularizing the JS code base, implementing JS on the web and how the modern HTML5 + JS APIs provide power to developers on the web. Finally, you will learn the deeper parts of the language, which include making JavaScript multithreaded with dedicated and shared web workers, memory management, shared memory, and atomics. It doesn’t end here; this book is 100% compatible with ES.Next. By the end of this book, you'll have fully mastered all the features of ECMAScript!

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Table of Contents (18 chapters)
Title Page
Title Page
PacktPub.com
PacktPub.com
Contributors
Contributors
Preface
Preface
Free Chapter
1
Getting Started with ECMAScript
Getting Started with ECMAScript
The let keyword
The const keyword
Immutability in JavaScript
Default parameter values
The spread operator
The rest parameter
Hoisting
Destructuring assignments
Arrow functions
Enhanced object literals
Trailing commas and JavaScript
The semicolon dilemma
Summary
2
Knowing Your Library
Knowing Your Library
Working with numbers
Doing math
Arrays
Collections
Objects
Summary
3
Using Iterators
Using Iterators
Symbols – primitive data type
The iteration protocol
Generator function
Tail call optimization
Summary
4
Asynchronous Programming
Asynchronous Programming
JavaScript execution model
The event loop
Writing asynchronous code
Promises and async programming
async/await – the future of asynchronous programming
Summary
5
Modular Programming
Modular Programming
JavaScript modules 101
Implementing modules – the old way
Implementing modules – the new way
Tree shaking
Using modules on the web
Summary
6
Implementing the Reflect API
Implementing the Reflect API
The Reflect object
Summary
7
Proxies
Proxies
Proxies in a nutshell
Working with the Proxy API
The uses of proxies
Summary
8
Classes
Classes
Understanding object-oriented JavaScript
Using classes
Using super in object literals
Summary
9
JavaScript on the Web
JavaScript on the Web
HTML5 and the rise of modern JavaScript
Modern JavaScript browser APIs
Summary
10
Storage APIs in JavaScript
Storage APIs in JavaScript
HyperText Transfer Protocol (HTTP)
Storing data with cookies
Working with localStorage
Working with SessionStorage
Handling storage changes across multiple tabs
Cookies versus local storage
The indexedDB - storing large data
Summary
11
Web and Service Workers
Web and Service Workers
An introduction to the concept of threads
Introduction to web workers
Checking if worker support is available
Working with dedicated web workers
Working with shared workers
Introduction to inline web workers
Same origin policy
Working with service workers
Summary
12
Shared Memory and Atomics
Shared Memory and Atomics
Basics of memory
What is shared memory?
Understanding parallel programming
What are atomics?
Fixing one billion count with atomics
A peek into Spectre
Summary
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Other Books You May Enjoy
Leave a review - let other readers know what you think
Index
Index

Working with service workers

Service workers! They finally give developers precise control of the network layer by creating a network proxy in JavaScript. Using service workers, you can intercept and modify network resource requests, handle how caching is done, and respond appropriately when the user's network is down.

Let us show, step-by-step, how to set up a service worker and its associated methods.

Prerequisites for service workers

Prerequisites for service workers are:

  • Because service workers are so powerful (almost like a network proxy) to avoid certain attacks, they're only available for domains running on HTTPS. However, they run fine on localhost, as well.
  • They heavily depend on promises, which we've already covered in depth in Chapter 4, Asynchronous Programming.

Checking for browser support

It is easy to check whether a client's browser supports service workers or not:

if('serviceWorker' in navigator) {
    // service worker available
    // lets code
}

Here, I'll assume that a service...

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