AJAX (Asynchronous JavaScript + XML) is a group of interrelated client- and server-side development technologies that allows parts of a webpage to be updated without having to reload the entire pageโthink of sites like YouTube, Google Maps, Gmail, and tabs within Facebook. It changed usability and the speed of web applications with its innovative concept: asynchronously exchanging small amounts of data with the server behind the scenes, without affecting the rest of the page.
AJAX makes features like drop-down menus, predictive text, auto-filled text, and more possible, all without clicking Refresh. What it means for servers is less stress on the network and faster operations. Thatโs the core benefit of AJAX-enabled sites: overall, theyโre more responsive and very efficient on both sides.
How does AJAX work?
AJAX calls are asynchronous, meaning theyโre made behind the scenes, independently from each other and the site as a whole. When a browser makes an AJAX call to the server, it isnโt stuck waiting for a response, halting all of the siteโs functionality. Instead, the web service on the server will send the data back to the browser once the task is completed, where client-side scripts will process the response and deliver it to the user.
AJAX breakdown
AJAX uses the following technologies:
- XML or JSON: the text-only format used to transfer data from server to browser script. Developers are increasingly using JSON over XML because of its native JavaScript compatibility.
- CSS: the language used to style how the data will look onscreen
- JavaScript: displays the data in the browser and processes user requests/interactions like clicks
- XMLHttpRequest objects: the keystone of AJAX, they actually retrieve the data with the server behind the scenes. All modern browsers support XMLHttpRequests.
Callbacks vs. Postbacks.
Pre-AJAX, the rules for client calls to the serverโbasically, anything the browser requests from a database to make a site responsiveโwere โpostbacks,โ plus server-side processing. Post-AJAX, the browser can โcallback,โ requesting small amounts of data directly from the serverโall without needing to wait for a postback.
Benefits of AJAX
- Better speed and performance
- More responsive, user-friendly websites and applications
- Ease of development, thanks to JSON, jQuery, and compilers that help to streamline complex JavaScript code
- Browser- and platform-independent. Also, Microsoft offers the AJAX Control Toolkit integrated into Visual Studio on the ASP.NET platform.
- Ideally implemented for updating small bits of information within a web application
- Allows text box autocomplete and predictive text
- Wonโt slow down with limited bandwidth. With AJAX callbacks, the server wonโt get overloaded by requests, which would otherwise cause the app to slow down.
AJAX is just one advancements in the front-end development landscapeโlearn more about front-end web development and how AJAX fits into the client-side technology landscape as a whole.