16.2. Rich Internet Applications (RIAs) with Ajax

Ajax improves the user experience by making interactive web applications more responsive. Consider a registration form with a number of fields (e.g., first name, last name e-mail address, telephone number, etc.) and a Register (or Submit) button that sends the entered data to the server. Usually each field has rules that the user’s entries have to follow (e.g., valid e-mail address, valid telephone number, etc.).

When the user clicks Register, an HTML5 form sends the server all of the data to be validated (Fig. 16.3). While the server is validating the data, the user cannot interact with the page. The server finds invalid data, generates a new page identifying the errors in the form and sends it back to the client—which renders the page in the browser. Once the user fixes the errors and clicks the Register button, the cycle repeats until no errors are found, then the data is stored on the server. The entire page reloads every time the user submits invalid data.