Welcome to Mastering JavaScript High Performance. In this book, we have covered JavaScript performance in a way that helps any JavaScript developer, whether they are new to the language or are experienced veterans. This book covers common performance bottlenecks, how to look for performance issues within code, and how to correct them easily.
We also review modern ways of optimizing our JavaScript code not just by relying on sheer knowledge of JavaScript, but by using tools to help optimize code for us. These tools include Gulp and Node.js, which help create great performing builds, and Jasmine, a JavaScript unit-testing framework that helps discover application flow issues in JavaScript. We also debug a hybrid app using Apple Xcode debugging tools for HTML and JavaScript.
Chapter 1, The Need for Speed, explains the need for faster JavaScript, discusses why JavaScript code is traditionally slow, and shows the types of code editors that can help us write faster JavaScript, without changing our coding style.
Chapter 2, Increasing Code Performance with JSLint, explores performance fixes in JavaScript, and covers JSLint, a very good JavaScript validation and optimization tool.
Chapter 3, Understanding JavaScript Build Systems, teaches you JavaScript build systems and their advantages for JavaScript performance testing and deployment.
Chapter 4, Detecting Performance, covers Google's Development Tools options and contains a review of how to use a Web Inspector to improve our JavaScript's code performance.
Chapter 5, Operators, Loops, and Timers, explains operators, loops, and timers in the JavaScript language and shows their effect on performance.
Chapter 6, Constructors, Prototypes, and Arrays, covers constructors, prototypes, and arrays in the JavaScript language and shows their effect on performance.
Chapter 7, Hands off the DOM, contains a review of the DOM in relation to writing high-performance JavaScript, and shows how to optimize our JavaScript to render our web applications visibly faster. We also take a look at JavaScript animation and test performance against modern CSS3 animation.
Chapter 8, Web Workers and Promises, demonstrates web workers and promises. This chapter also shows you how to use them, including their limitations.
Chapter 9, Optimizing JavaScript for iOS Hybrid Apps, covers optimizing JavaScript for mobile iOS web apps, (also known as hybrid apps). Also, we take a look at the Apple Web Inspector and see how to use it for iOS development.
Chapter 10, Application Performance Testing, introduces Jasmine, a JavaScript testing framework that allows us to unit-test our JavaScript code.
For this book, you will need a basic understanding of JavaScript, how to write functions and variables in JavaScript, how to use basic web technologies such as HTML and CSS, as well as some basic debugging skills using a Web Inspector such as Chrome Developer tools or Firebug, to name a few.
You will need a text editor, preferably for HTML and JavaScript coding; the available choices are covered in Chapter 1, The Need for Speed. Choosing the editor and the admin rights to the system you're working on is up to you, and it also depends on your budget. Also, Chapter 9, Optimizing JavaScript for iOS Hybrid Apps, strictly covers JavaScript in iOS development; for that, you will need a copy of Xcode and an Intel-based Mac. If you don't have these, you can still read along but, ideally, most of this work is done with a Mac.
This book is written for intermediate JavaScript developers. If you are experienced with unit-testing JavaScript and writing your own frameworks, and are able to understand what instance-based versus static-based is in JavaScript, this book may not be for you. Also, if you're very new to JavaScript—as in, "How do I use a function?"—I recommend looking for a beginner's JavaScript book as well.
However, if you've been into JavaScript for a while but are new to node-style performance testing, grunt or gulp project deployments, and unit-testing in JavaScript, or if you want to know more on how to write JavaScript faster, or if you're just looking to stop your code base from lagging behind without reworking your coding style, you are reading the right book.
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 explanations of their meanings.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "To solve this issue, modern browsers have implemented new console functions called console.time and console.timeEnd."
A block of code is set as follows:
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Jasmine Spec Runner v2.1.3</title>
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: "Clicking on the Next button moves you to the next screen."
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