C H A P T E R  15

JSON and Ajax

Web pages have evolved over recent years, mimicking the functionality found on desktop applications. Despite the added complexity, the user experience has greatly improved; developed sites feel more responsive and engaging. Through quicker feedback, popup tips, auto-completion, and fewer necessary full-page reloads, browsing is a richer, more intuitive, and enjoyable experience.

What makes this all possible is the technique of issuing asynchronous requests from the browser to the server and receiving back responses. The requests are asynchronous because they are done in separate threads that do not block the main script execution. Information is passed back and forth in the form of JSON (JavaScript Object Notation), XML (eXtensible Markup Language), or plain text. This asynchronous communication between browser and server does not require a full page reload and is known as Ajax.