Chapter 12. JavaScript in Web Browsers

The first part of this book described the core JavaScript language. Now we move on to JavaScript as used within web browsers, commonly called client-side JavaScript.^[1] Most of the examples we've seen so far, while legal JavaScript code, had no particular context; they were JavaScript fragments that ran in no specified environment. This chapter provides that context. It begins with a conceptual introduction to the web browser programming environment and basic client-side JavaScript concepts. Next, it discusses how we actually embed JavaScript code within HTML documents so it can run in a web browser. Finally, the chapter goes into detail about how JavaScript programs are executed in a web browser.

^[1] The term "client-side JavaScript" is left over from the days when JavaScript was used in only two places: web browsers (clients) and web servers. As JavaScript is adopted as a scripting language in more and more environments, the term client-side makes less and less sense because it doesn't specify the client side of what. Nevertheless, we'll continue to use the term in this book.