The following are scenarios where it’s more likely to be beneficial to use AJAX functionality:
Highly interactive applications - where an application is highly interactive, it may provide benefits to use AJAX to allow the interactivity without the time cost of page reloads. A good example of a highly interactive web site is Google Maps.
Parts of pages – AJAX is best used in key places throughout a web site where it adds significant value. There is little or no value in using AJAX to provide the majority of your page content – you may lose browser compatibility, make the application overly complex and cause problems with the site being indexed in search engines.
Intranets – on an internal web site the bandwidth is much higher so more AJAX usage can be successful. It’s often the case that intranets involve working with data, and this is often a good application for AJAX.
Online wizards – linear user interfaces that collect a large series of data are a well-known challenge in web applications, and can be implemented using AJAX in a way where the user feels more in control and the application is more responsive.
Data input & validation – before AJAX it was hard to build anything resembling rich data input forms that give clear and accurate feedback to users. With AJAX it’s possible to validate the data the user enters, while they are entering it. They can then receive feedback (using the server’s intelligence) without the page being posted back. For example an email validation field could check if the email address is valid using the DNS, without the user knowing.
Data visualization – visualizing large datasets on the web can be difficult because there’s been no easy way to pull in more data as the user needs it. With AJAX it’s possible to show a view on the data, and simply load more in as needed. Again, Google Maps is a great example.
Here are some top tips for things you should consider when using AJAX:
Give visual feedback - When a user clicks on something in the AJAX user interface, they need immediate visual feedback, just like when a button presses in on a standard form. Immediate feedback helps users, and makes them more efficient.
Keep the Back button – make sure that the Back button in your application functions on every page of the site.
Use links for navigation – avoid the temptation to use links as an interface on your AJAX application to change the state of your application. Users have been trained over ten years to expect a link to “take” them somewhere, so give them what they expect.
Limit the scope of visual changes – when an AJAX call results in one or more changes to what the user sees, keep the changes local to the place where the user would expect them to be.
Use human-readable links – people like to pass the addresses of useful web pages to each other. Make sure your application supports URLs that people can share easily, so not too long or complex.
Don’t bloat the code – make sure that your application uses as little client-side scripting as possible. This reduces download time for the page and also reduces the processor requirements on the client browser, so results in a faster browser experience.
Follow UI conventions – AJAX is a world of possibilities, but when it comes to user interface the best is invariably the familiar. If you’re creating a user interface for a specific feature, the place to start is by replicating an existing successful interface and looking at what your clients expect. Also remember that although it may be cool to implement drag-and-drop, few people may realize the interface relies on it.
Don’t scroll – users like to feel in control, so if they have moved the scrollbar to a specific place, don’t move the page somewhere else.
Reduce page loads – do as much as you can to reduce the number of page loads the user has to do to achieve their goal.
Original Source: How and When to Use AJAX
