AJAX Interview Questions
AJAX Interview Tips
AJAX is a type of programming made popular in 2005 by Google (with Google Suggest).
AJAX is not a new programming language, but a new way to use existing standards.
With AJAX you can create better, faster, and more user-friendly web applications.
Advantages OF Ajax
In many cases, related pages on a website consist of much content that is common between them. Using traditional methods, that content would have to be reloaded on every request. However, using Ajax, a web application can request only the content that needs to be updated, thus drastically reducing bandwidth usage and load time. The use of asynchronous requests allows the client’s Web browser UI to be more interactive and to respond quickly to inputs, and sections of pages can also be reloaded individually. Users may perceive the application to be faster or more responsive, even if the application has not changed on the server side. The use of Ajax can reduce connections to the server, since scripts and style sheets only have to be requested once.
Disadvantages of Ajax.
Pages dynamically created using successive Ajax requests do not automatically register themselves with the browser’s history engine, so clicking the browser’s “back” button may not return the user to an earlier state of the Ajax-enabled page, but may instead return them to the last full page visited before it.
Workarounds include the use of invisible IFrames to trigger changes in the browser’s history and changing the anchor portion of the URL (following a #) when AJAX is run and monitoring it for changes.
Dynamic web page updates also make it difficult for a user to bookmark a particular state of the application. Solutions to this problem exist, many of which use the URL fragment identifier (the portion of a URL after the ‘#’) to keep track of, and allow users to return to, the application in a given state.
The same origin policy prevents Ajax from being used across domains, although the W3C has a draft that would enable this functionality.
The lack of a standards body behind Ajax means there is no widely adopted best practice to test Ajax applications. Testing tools for Ajax often do not understand Ajax event models, data models, and protocols. Opens up another attack vector for malicious code that web developers might not fully test for.