Pop-up blockers are very common place these days, and for a good reason: pop-ups are annoying. Using light boxes, which are pop-ups inside the browser window, the pop-up blocker can’t stop it, and they aren’t quite as irritating to the user. Some people use them for advertising, like on Darren Rowe’s ProBlogger.com. They can also be used for something like a login or register box, like Reddit does when you try to vote and you are not logged in.
Creating a clean, slick user interface is a very popular use of AJAX. It allows users to accomplish more on a single page. The benefits of this are twofold: First, it makes using the web application quicker and easier for the user; Secondly, it cuts down on the number of requests you have to make to the server, which cuts down on bandwidth and load times. A free file upload service called Drop.io uses this well. Google has also really pushed the envelope of what is possible with AJAX by making desktop-like applications like Google Docs and Google Maps.
Chatting online has come a long way from the days of IRC. Chat rooms and instant messaging can now be handled in the browser completely. There are two main AJAX processes in a chat room or IM application. Think of one of them as your ears, and one of them as your mouth. Your ‘mouth’ updates the server and lets it know that you have sent a message. The ‘ears’ check with the server constantly, and updates your page with messages that have been sent by whoever you are chatting with.
Forms have always tricky to work with, but AJAX can make them a lot better for the users. AJAX can be used in a variety of ways, from the auto complete mentioned above, to validation and submission as well. Some sites use AJAX to check if a form meets certain requirements, such as password strength, or if something is a valid email or URL.
One of the things that made Twitter so popular was their simple and easy-to-use interface. When someone makes a ‘tweet’, it is instantly added to their feed, and everything is updated. Recently, Twitter has started using AJAX with their ‘trending topics’ pages. Every few seconds, the page lets the user know that more tweets have been made about the subject, giving them up-to-the-second updates.
Social bookmarking sites like Digg and Reddit let the users decide the main content of the site by voting on content that the users like. They use AJAX to handle all of the voting, so that the users are able to voice their opinions on a number of stories quickly and easily.
Google was one of the first major companies to start using AJAX, and Google’s search suggestion tool was one of the first ways they used it, and one of the first auto-complete tools made. When typing into the Google search bar, it starts to use AJAX to get common results from the database on each keystroke. Auto-Complete is great for forms where you have a lot of possible inputs, and making a select drop down would be too long and cumbersome.
Instead of going to a login page, and then navigating back to the page you originally wanted, with AJAX, a user can type in their user name and password directly into the original page. From there AJAX will send a request to the server to log them in. The server let’s the page know they have been logged in, and the page you are on can update as needed. Digg has a login-system that works like this.