What is AJAX? Understanding Asynchronous JavaScript and XML

What is AJAX?

AJAX stands for Asynchronous JavaScript and XML. It is a group of related technologies used to display data asynchronously. In other words, it sends and retrieves data without reloading the web page.

What are the advantages of AJAX?

• Quick Response
• Bandwidth utilization
• The user is not blocked until data is retrieved from the server.
• It allows us to send only important data to the server.
• It makes the application interactive and faster.

 What are the disadvantages of AJAX?

• Dependent on JavaScript
• Security issues
• Debugging is difficult

What are the real web applications of AJAX currently running in the market?

• Twitter
• Facebook
• Gmail
• Javatpoint
• Youtube

What are the security issues with AJAX?

• AJAX source code is readable
• Attackers can insert the script into the system

What are the technologies used by AJAX?

• HTML/XHTML and CSS - These technologies are used for displaying content and style.
• DOM - It is used for dynamic display and interaction with data.
• XML - It is used for carrying data to and from server
• XMLHttpRequest - It is used for asynchronous communication between client and server.
• JavaScript - It is used mainly for client-side validation

What is the purpose of XMLHttpRequest?

• It sends data in the background to the server.
• It requests data from the server.
• It receives data from the server.
• It updates data without reloading the page.

What are the properties of XMLHttpRequest?

The important properties of the XMLHttpRequest object are given below.

• onReadyStateChange - It is called whenever readystate attribute changes.
• readyState - It represents the state of the request.
• responseText - It returns response as text.
• responseXML - It returns response as XML.
• status - It returns the status number of a request.
• statusText - It returns the details of status.

What are the important methods of XMLHttpRequest?

• abort() - It is used to cancel the current request.
• getAllResponseHeaders() - It returns the header details.
• getResponseHeader() - It returns the specific header details.
• open() - It is used to open the request.
• send() - It is used to send the request.
• setRequestHeader() - It adds request header.

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.

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

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

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

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

What are the common AJAX frameworks?

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

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.

What is the difference between JavaScript and AJAX?