AJAX was invented primarily to send and receive data without having to reload the web pages. This helps make the application quick and more interactive. When applying for a job role that requires proficiency in AJAX, candidates should be completely familiar with all its functions. This is when having access to the common AJAX interview questions can be immensely beneficial in preparing for the interview. With that said, here are the 22 common interview questions related to AJAX, along with some frequently asked questions to help you prepare well for the interview process. 

Top AJAX Interview Questions and Answers for 2024

1. What are the different technologies used in AJAX?

There is a range of technologies that are used in AJAX, such as HTML, XHTML, CSS, XML, XSLT, JSON, JavaScript, and various other APIs.

2. What is a synchronous request in AJAX?

There are two types of requests used in AJAX on the basis of request priority. The request that waits for the response from the server after requesting to proceed with the script execution’s next part is called a synchronous request. It is essential to use a synchronous request mechanism in certain cases when it is inevitable. However, it should also be avoided, if possible, in order to make sure the server is highly responsive.

3. What is an asynchronous request in AJAX?

An asynchronous request in AJAX moves forward with the next line of script execution without waiting for the web server after a request. This can later be handled when the web server sends a response. Since users can interact with web pages without having to wait for the responses from the server, an asynchronous request is considered extremely important as it allows for a prompt response to users without any delay.

4. What are the limitations of AJAX?

AJAX has certain limitations, which have been listed below-

  • While AJAX is a preferred choice for websites, it is not recommended to use AJAX for web application development.
  • While AJAX has many advantages, the process of developing web pages might be complex and time-consuming.
  • Since crawlers fail to identify the web applications developed using AJAX and JavaScript, it is not possible for search engines to index pages that are developed with the help of AJAX.
  • Pages developed with the help of AJAX cannot be bookmarked.
  • If JavaScript is disabled in a browser, AJAX does not function.
  • Since different page controls have different loading times, it results in a slow response time for AJAX.

5. List AJAX features.

Here are some of the salient features of AJAX-

  • It offers high-performing web pages and a range of features that are user-friendly, such as autocomplete suggestions.
  • It allows for client-side template rendering.
  • With AJAX, users can interact with web pages efficiently without being interrupted by constant reloading of the web pages.
  • It is server independent and has a rich user interface.
  • It supports live data binding and supports data view control.

6. What are the security threats with AJAX codes?

When using AJAX codes, the following are the security threats that a web page may be exposed to-

  • Since AJAX request calls are in plain format, this may result in insecure access to the database.
  • Anyone can view the data retrieved on a web page made using AJAX as the retrieved data is stored on the client browser.
  • Web pages made using AJAX might be extremely vulnerable to cyber attacks by hackers as the entire AJAX code is easily visible using the view page source. These codes, when accessed by hackers, can be misused.

7. What is XMLHttpRequest?

XMLHttpRequest is an API with various properties and methods that are used by several scripting languages, such as VBScript and JavaScript. These methods are useful for the manipulation and transfer of XML data with the help of HTTP protocol which enables the connection between the client and server.

XMLHttpRequest supports various formats for transferring data, including JSON, XML, plain text, and binary content. With XMLHttpRequest, you can update different parts of a webpage without requiring reloading of the page.

8. What is the AJAX callback function?

The AJAX callback function has various steps, which start with a request sent by the client browser to the server. However, since the request sent is asynchronous in nature, the user can carry on without having to wait for the server to respond to the request. Once the server receives the message, it processes the page with the AJAX callback and sends the response in the form of a JavaScript code string. This code string then is executed in the browser.

9. What is ScriptManager in ASP.Net?

ScriptManager in ASP.Net is responsible for managing a variety of AJAX resources, which is why it has a central role to play in AJAX functionalities. Some of the resources managed by ScriptManager are coordinating partial page uploads and downloading the Microsoft AJAX library.

10. What is the difference between ScriptManager and ScriptManagerProxy?

While ScriptManager is responsible for functionalities that enable the rendering of partial pages and the Microsoft AJAX library, ScriptManagerProxy is responsible for enabling nested components for adding script and service references when a page has ScriptManager control.

11. How can we cancel the current request in AJAX?

When a user performs an action that results in the setting off of an AJAX request, the current request on AJAX gets canceled.

12. Are XMLHttpRequest and AJAX the same thing?

No, XMLHttpRequest is a component of the AJAX equation. It is that aspect of AJAX that is responsible for making the asynchronous server communication viable.

13. What is the importance of client-side libraries?

Similar to the ASP.Net programming model, client-side libraries help with handling issues with browser compatibility and making request calls that are asynchronous in nature over XMLHttp.

14. What is AJAX Control Toolkit?

AJAX Control Toolkit is useful for the extension of ASP.Net control functionalities. AJAX Control Toolkit makes use of JavaScript codes for enhancing the ASP.Net capabilities and controls. With this control toolkit, you can write extenders and controls that are reusable, customizable, and extensible. And with this, you can create an interactive web experience.

15. When are the AJAX GET and AJAX POST requests used?

The AJAX GET request and POST request are used in certain scenarios. The AJAX GET request should be used when no change in the data for the given URL is requested. Likewise, HTTP POST should be used for a server’s updated state and for consistent web application architecture.

16. What is an update panel?

Update panel, which is a server control, finds its applications in updating a certain portion of a web page. Whenever you use the update panel, you also need to use ScriptManager. However, the update panel does not allow handling outside controls.

17. What are the types of triggers present in the update panel?

The update panel consists of two types of triggers. The PostBackTrigger is used as a full postback and it does not function in an asynchronous manner. The second type of trigger is AsyncPostBacktrigger, which is responsible for partial postback in an asynchronous way.

18. What are the prerequisites for executing AJAX applications on a server?

Executing the AJAX application simply requires installing Microsoft Visual Studio 2010. However, if you intend to use extenders in your application, you will also need to install AJAX Control Toolkit. Once you have installed the control toolkit, you then have to copy the AjaxControlTookit.dll file to your application’s Bin directory.

19. How can you determine if an AJAX request has been completed?

To check if an AJAX request has been successfully completed, you need to use the ReadyState property. The request is completed when the property is equal to four.

20. What are the types of postbacks in AJAX?

There are two types of postbacks in AJAX, which are synchronous postback and asynchronous postback.

21. What are the components of the ASP.Net AJAX client library?

The AJAX client library comprises three components, which are the component layer, the core services layer, and the browser compatibility layer.

22. What are the goals of AJAX?

The basic goals of AJAX are to reduce web server hits and network load while providing an interactive user interface. It is also used for neutral platforms and architecture and to offer support for both asynchronous and synchronous communications.

Frequently Asked Questions

1. What is the main use of AJAX?

The main use of AJAX is to update web pages. This is made possible through asynchronous exchange of small amounts of data behind the scenes with the server, because of which, updating the web pages without reloading the whole page is made possible.

2. How can you test the AJAX code?

AJAX codes can be tested with the help of JUnit, which is an open-source testing framework. Before you test your AJAX codes, you need to create test cases.

3. What server supports AJAX?

All modern-day browsers and servers, such as Google Chrome, Mozilla Firefox, Internet Explorer 5.0 and above, Opera 7.6 and above, Safari 1.2 and above, and Netscape 7.1 and above support AJAX.

4. What are the controls of AJAX?

The controls of AJAX include ScriptManager, ScriptManagerProxy, Timer, UpdateProgress, and UpdatePanel. 

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