JavaScript and the Document Object Model

As mentioned in Chapter 1, JavaScript is the heart of AJAX. JavaScript has a similar syntax to the good old C language. JavaScript is a parsed language (not compiled), and it has some Object‑Oriented Programming (OOP) capabilities. JavaScript wasn’t meant for building large powerful applications, but for writing simple scripts to implement (or complement) a web application’s client-side functionality (however, new trends are tending to transform JavaScript into an enterprise-class language—it remains to be seen how far this will go).

JavaScript is fully supported by the vast majority of web browsers. Although it is possible to execute JavaScript scripts by themselves, they are usually loaded on the client browsers together with HTML code that needs their functionality. The fact that the entire JavaScript code must arrive unaltered at the client is a strength and weakness at the same time, and you need to consider these aspects before deciding upon...