AJAX - Interview Questions and Answers

11) What are the types of open() method used for XMLHttpRequest?

open(method, URL) - It opens the request specifying get or post method and URL.
open(method, URL, async) - It is same as above but specifies asynchronous or not.
open(method, URL, async, username, password) - It is same as above but specifies the username and password.

12) What are the types of send() method used for XMLHttpRequest?

send() - It sends get request
send(string) - It sends post request.

13) What is the role of the callback function in AJAX?

The callback function passes a function as a parameter to another function. If we have to perform various AJAX tasks on a website, then we can create one function for executing XMLHttpRequest and a callback function to execute each AJAX task.

14) What is JSON in AJAX?

JSON stands for JavaScript Object Notation. In AJAX, it is used to exchange data between a browser and a server. It is easy to understand, and data exchange is faster than XML. It supports array, object, string, number, and values.

 request.onreadystatechange  = function(){         if (request.readyState == 4  )         {           var jsonObj = JSON.parse(request.responseText);//JSON.parse() returns JSON object           document.getElementById("date").innerHTML =  jsonObj.date;           document.getElementById("time").innerHTML = jsonObj.time;         }      } 

15) What are the tools for debugging AJAX applications?

There are several tools for debugging AJAX applications.

Firebug for Mozilla Firefox
Fiddler for IE (Internet Explorer)
JavaScript HTML Debugger
MyEclipse AJAX Tools
Script Debugger

16) What are the types of post back in AJAX?

There are two types of post back in AJAX.

Synchronous Postback - It blocks the client until the operation completes.

Asynchronous Postback - It doesn?t block the client.

17) What are the different ready states of a request in AJAX?

There are 5 ready states of a request in AJAX.

0 means UNOPENED
1 means OPENED
2 means HEADERS_RECEIVED
3 means LOADING
4 means DONE

18) What are the common AJAX frameworks?

Dojo Toolkit
YUI
Google Web Toolkit (GWT)
Spry
MooTools
Prototype

19) How can you test the AJAX code?

JUnit is the open source unit testing framework for client-side JavaScript. It is required to create test cases. The unit test case is a code which ensures that the program logic works as expected.

20) What is the difference between JavaScript and AJAX?

JavaScript is an object-based scripting language.	AJAX is a group of inter-related technologies like JavaScript, XML, HTML, CSS etc
It requests the server and waits for the response.	It sends a request to the server and doesn't wait for the response.
It consumes more bandwidth as it reloads the page.	It doesn't reload the page so consumes less bandwidth.

Interview :: AJAX