To get the most out of this book

All the code samples in this book are written in modern JavaScript, adopting syntax up to ES2017, including Promises and async/await. Nevertheless, the concepts presented in this book can be leveraged by developers working with other programming languages and frameworks, too.

In the first six chapters, we are assuming that all JavaScript code runs in a Node.js environment, for example, in a server-side application or using frameworks such as Electron. The minimum version of Node.js that is capable of running every code sample in this book is 15; however, we recommend using Node.js 16 (the current LTS as of writing) or higher.

The last two chapters include JavaScript code that is meant to be executed inside a web browser, using APIs that are available in recent versions of all modern desktop and mobile browsers, including Chrome, Edge, Firefox, Safari, or another Chromium-based browser (notably, Internet Explorer is not supported). It's assumed that the code will be included in frontend applications packaged with a bundler such as Webpack, Rollup, or esbuild (the usage of those tools falls outside the scope of this book). More information on browser support and links to compatibility tables are included in the Technical requirements section of Chapter 7, Introduction to Cryptography in the Browser. For development and experimentation with frontend code, we have also provided a "playground" that can run inside a web browser: https://bit.ly/crypto-playground.

If you are using the digital version of this book, we advise you to type the code yourself or access the code from the book's GitHub repository (a link is available in the next section). Doing so will help you avoid any potential errors related to the copying and pasting of code.