In order to get the most out of this book, it is useful to have a basic understanding of the JavaScript language and to have some experience of atleast one platform in which JavaScript is utilized. This may include the browser or Node.js, for example.

In order for you to execute the pieces of code shared within the book, you have a few options available:

• Create an HTML file with <script> in which you can place any JavaScript code you wish to test. In order to observe an output visually, you can either use alert() or console.log(). In order to view values outputted via console.log(), you can open the development tools of the browser.
• Directly open the development tools of any modern browser and directly type JavaScript expressions and statements into the JavaScript console. A guide to doing this within the Chrome browser can be found here: https://developers.google.com/web/tools/chrome-devtools/console/javascript.
• Create a test.js file and run it via Node.js or use the Node.js REPL to interactively test distinct JavaScript statements and expressions via the command line. A comprehensive guide to getting started with Node.js can be found here: https://nodejs.org/en/docs/guides/getting-started-guide/.

Browser development tools are accessible within all modern browsers. The shortcuts are as follows:

• In Chrome: Ctrl + Shift + J on Windows or CMD + Shift + J on macOS
• In Firefox: Ctrl + Shift + I or F12 on Windows and Linux, or CMD + OPTION + I on macOS
• In IE: F12 on Windows

You are advised to move through the book at your own pace and conduct additional research and exploration online if you are finding a topic hard to grasp. Some especially helpful resources include the following:

• Mozilla Developer Network: https://developer.mozilla.org/en-US/docs/Web/JavaScript
• ECMAScript Language Specification: https://www.ecma-international.org/publications/standards/Ecma-262.htm

The book gets progressively more detailed as you advance through it, so it is natural to take a slower pace in later chapters. This may be especially true for Chapters 6-12, which cover, in great detail, the characteristics of the JavaScript language itself.

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

You can download the code files by following these steps:

1. Log in or register at www.packt.com.
2. Select the Support tab.
3. Click on Code Downloads.
4. Enter the name of the book in the Search box and follow the onscreen instructions.

Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:

• WinRAR/7-Zip for Windows
• Zipeg/iZip/UnRarX for Mac
• 7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Clean-Code-in-JavaScript. In case there's an update to the code, it will be updated on the existing GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: https://static.packt-cdn.com/downloads/9781789957648_ColorImages.pdf.

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "We find a publicly available package called shipping_address_validator and decide to use it."

A block of code is set as follows:

function validatePostalCode(code) {
  return /^[0-9]{5}(?:-[0-9]{4})?$/.test(code);
}

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

npm install --save react react-dom

Bold: Indicates a new term, an important word, or words that you see on screen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "For the purposes of our case study, the plant names only exist as their full Latin names, which includes a family (for example, Acanthaceae)."