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.