How do I decide when to use AJAX?

Using AJAX to manage the size of web pages

There are many times, especially when a data exists in tabular form, where supplemental data is useful to the viewer, but not to every viewer. In those cases, AJAX can improve the user experience for those, who desire additional information, while not affecting the user experience, for those who don't. For example, suppose a web page displays the district-by-district election results for your state. As you cursor over each district, a complete description of the voting results is displayed, including exhaustive details on voting patterns, demographics, etc. This information could have been downloaded with the initial page flow, but at the cost of a larger initial download. Considering that not every viewer will want this information, it could be argued that it is better to download the election details as needed with AJAX.

Using AJAX to create context sensitive controls

Another very effective use of AJAX is where a series of form controls are dependent on previous selections. In this case, imagine a form that needs to capture Country and City information in select list controls. The first select list contains a list of countries. On selection of the country, the second control uses an AJAX function to request the list of cities for the selected country, and dynamically assembles a relevant list of cities for only that country in the second select list. This could, again, be done without the use of AJAX, but all possible combinations of country-state select lists would need to be part of the initial download.

AJAX can kill bookmarking

When AJAX is responsible for massive content changes that otherwise would be done with traditional navigation, you loose the ablity to bookmark (or share a link to) the page. In short, the user experience will be diminished if the URL doesn't define the content of teh web page.

AJAX may disable the browser back key

Web surfers rely on the utility and dependability of the the browser's back button, or the ability to revert to the previous page by “clicking back”. When the content is controlled by AJAX, the back button becomes useless and the user experience is compromised.

AJAX challenges Search Engine Optimization

Modern search engines rank pages , or decide how relevant your content is, by examining the content. If the content is dependent on user interaction and is downloaded well after the initial page, the only thing search engines will have to identify your content are the keywords, which are losing their effectiveness in SEO.

When is data loading?

Perhaps the biggest complaint against AJAX is that is it often not well implemented, and it is next to impossible to tell when your browser is hung up, or when it is simply waiting for an AJAX download to complete. This is because the familiar animated browser download icon doesn't respond to AJAX commands.