AJAX interview questions for fresher/AJAX Interview Questions and Answers for Freshers & Experienced

Which are the two methods used for cross domain Ajax calls?

There are two methods used to transfer data between the two more more security domains:

CORS – Cross Origin Resource Sharing and it works with the HTTP web browsers.
JSONP – JSON with Padding which works with the HTTP GET and on legacy browsers.

How to cancel the current request in Ajax?

Current request in AJAX is cancelled when the user performs an action which sets off an Ajax request. This can be depicted with the help of auto-complete functionality for a search box where users can be helped with related search terms based on their current input, by making an AJAX request each time they pass a key in the search field. The user types faster than the Ajax request and you would want to abort any non-finished requests, before starting the next one.

Is Adaptive Path selling Ajax components or Trademarking the name? Where can I download it?

Ajax isn’t something you could download. It’s a method — a manner of considering the structure of net programs and the use of sure technology. Neither the Ajax call nor the method is proprietary to Adaptive Path.

Should I use an Http get or Post for my Ajax Calls?

AJAX requests need to use an HTTP GET request whilst retrieving records wherein the records will now no longer extrude for a given request URL. An HTTP POST needs to be used whilst a nation is up to date at the server. This is in keeping with HTTP idempotency pointers and is exceedingly encouraged for a constant net utility structure.

Are there any Frameworks available to help Speedup Development with Ajax?

There are numerous browser-aspect frameworks available, every with its uniqueness…

Should I use Xml or Text, Javascript, or Html as a Return Type?

It depends. The ‘X’ in AJAX stands for XML, however numerous AJAX proponents are short to factor out that not anything in AJAX, in keeping with se, precludes the use of different varieties of payload, inclusive of JavaScript, HTML, or simple textual content.

HTML – Injecting server-generated HTML fragments without delay right into a file is usually a completely powerful AJAX technique. However, it is able to be complex to maintain the server-aspect aspect in sync with what’s displayed at the consumer.

XML – Web Services and AJAX appear made for one any other. You can use consumer-aspect API for downloading and parsing the XML content material from RESTful Web Services. (However bear in mind with a few SOAP-primarily based totally Web Services architectures the payloads can get pretty massive and complicated, and consequently can be irrelevant with AJAX strategies.)

Plain Text – In this case, server-generated textual content can be injected right into a file or evaluated through consumer-aspect common sense.

JavaScript – This is an extension to the apparent textual content case with the exception that a server-aspect aspect passes a fraction of JavaScript inclusive of JavaScript item declarations. Using the JavaScript eval() feature you could then create the items at the consumer. JavaScript Object Notation (JSON), that’s a JavaScript item-primarily based totally records trade specification, is based on this technique.

Is it possible to set session variables from Javascript?

No, It’s now no longer viable to set any consultation variables without delay from javascript as it’s merely a consumer-aspect generation. You can use AJAX even though it is asynchronous.

Did adaptive path invent Ajax? Did Google? Did adaptive path help build Google’s Ajax Applications?

If you haven’t selected a framework, but it’s encouraged, don’t forget to use JavaServer Faces or a JavaServer Faces-primarily based framework. JavaServer Faces additives may be created and used to summarise most of the information of producing JavaScript, AJAX interactions and therefore allow easy AJAX utilized by JSF utility builders plug-ins in JSF well suited IDE’s, inclusive of Sun Java Studio Creator.

Neither Adaptive Path nor Google invented Ajax. Google’s current merchandise is the highest-profile example of Ajax programs. Adaptive Path changed into now no longer worried withinside the improvement of Google’s Ajax programs. However, we were doing Ajax paintings for a number of our different customers.

What is update panel?

Update panel is a server control used to update the specified portion of a web page. Script Manager needs to be used whenever update panel is used. Using update panel, user cannot handle outside controls.

What Exactly Is The W3c Dom?

The W3C Document Object Model (DOM) is defined by the W3C as the following: The Document Object Model is a platform- and language-neutral interface.

How Do I Test My Ajax Code?

There is a port of JUnit for client-side JavaScript called JsUnit.

How Do I Submit A Form Or A Part Of A Form Without A Page Refresh?

When creating a form make sure that the "form" element "onSubmit" attribute is set to a JavaScript function that returns false.

<form onSubmit="doAJAXSubmit();return false;" >
<input type="text" id="tf1" />
<input type="submit" id="submit1" value="Update"/>
</>
You can also submit data by associating a function with a form button in a similar way.

<form onSubmit="doAJAXSubmit();return false;" >
<input type="text" id="tf1" />
<input type="button" id="button1" onClick="doAJAXSubmit()" value="Update"/>
</>
Note that the form "onSubmit" attribute is still set. If the user hits the enter key in the text field the form will be submitted so you still need to handle that case.

When updating the page it is recommend you wait to make sure that the AJAX update of the form data was successful before updating the data in the page. Otherwise, the data may not properly update and the user may not know. I like to provide an informative message when doing a partial update and upon a successful AJAX interaction I will then update the page.

Whats With The -alpha In The Install Instructions?

HTML_AJAX hasn't had a stable release yet and the pear installer doesn't install non stable packages by default unless you specify a version.

When Do I Use A Synchronous Versus Asynchronous Request?

They don't call it AJAX for nothing! A synchronous request would block in page event processing and I don't see many use cases where a synchronous request is preferable.

Some Of The Google Examples You Cite Don't Use Xml At All. Do I Have To Use Xml And/or Xslt In An Ajax Application?

No. XML is the most fully-developed means of getting data in and out of an Ajax client, but there’s no reason you couldn’t accomplish the same effects using a technology like JavaScript Object Notation or any similar means of structuring data for interchange.

How Do We Debug Javascript?

There are not that many tools out there that will support both client-side and server-side debugging. I am certain this will change as AJAX applications proliferate. I currently do my client-side and server-side debugging separately. Below is some information on the client-side debuggers on some of the commonly used browsers.

* Firefox/Mozilla/Netscape - Have a built in debugger Venkman which can be helpful but there is a Firefox add on known as FireBug which provides all the information and AJAX developer would ever need including the ability to inspect the browser DOM, console access to the JavaScript runtime in the browser, and the ability to see the HTTP requests and responses (including those made by an XMLHttpRequest). I tend to develop my applications initially on Firefox using Firebug then venture out to the other browsers.
* Safari - Has a debugger which needs to be enabled. See the Safari FAQ for details.
* Internet Explorer - There is MSDN Documentation on debugging JavaScript. A developer toolbar for Internet Explorer may also be helpful.
While debuggers help a common technique knowing as "Alert Debugging" may be used. In this case you place "alert()" function calls inline much like you would a System.out.println. While a little primitive it works for most basic cases. Some frameworks such as Dojo provide APIs for tracking debug statements.

Should I Use An Http Get Or Post For My Ajax Calls?

AJAX requests should use an HTTP GET request when retrieving data where the data will not change for a given request URL. An HTTP POST should be used when state is updated on the server. This is in line with HTTP idempotency recommendations and is highly recommended for consistent web application architecture.

Reliance on JavaScript

Ajax relies on JavaScript, which is often implemented differently by different browsers or versions of a particular browser. Because of this, sites that use JavaScript may need to be tested in multiple browsers to check for compatibility issues.

Is Adaptive Path Selling Ajax Components Or Trademarking The Name? Where Can I Download It?

Ajax isn’t something you can download. It’s an approach — a way of thinking about the architecture of web applications using certain technologies. Neither the Ajax name nor the approach is proprietary to Adaptive Path.

What Is The Difference Between Proxied And Proxyless Calls?

Proxied calls are made through stub objects that mimic your PHP classes on the JavaScript side. E.g., the helloworld class from the Hello World example.

Proxyless calls are made using utility javascript functions like HTML_AJAX.replace() and HTML_AJAX.append().

What are the types of post back in Ajax?

There are 2 types of post back in AJAX.

Asynchronous - It does not block the client.
Synchronous - It blocks the client until the operation completes.

What is an Ajax call?

It’s an asynchronous request initialized by the browser that doesn’t directly result in a page transition. In an AJAX call, AJAX communicates with the server using the XMLHttpRequest object.

What is readyState in Ajax?

In AJAX, the readyState is a function to be called when the readyState property changes. It holds the status of the XMLHttpRequest.

What is the primary use of Ajax?

The primary use of AJAX is to allow the client side of an application to communicate with the server side of the application effectively. It’s the first technique available in which the client side of a web application to communicate directly with the server.

What is asynchronous request in AJAX?

In AJAX, the asynchronous request is used to block the client until the targeted operation completes. When a reply is received a browser event is fired, which allows the scripts to execute associated actions.

What is Cache false in Ajax call?

The cache: false is used by developers to prevent all future AJAX requests from being cached, regardless of which jQuery method they use. We can use $.ajaxSetup({cache:false}); to apply the technique for all AJAX functions.

How to know that an Ajax request has completed?

To know the status of an AJAX request, developers use ready State. It allows users to determine the request status. It the value comes 4, then the application has been completed, and the response is sent to the browser.

What is the use of XMLHttpRequest in Ajax?

In AJAX, the XMLHttpRequest (XHR) is an API that can be used by JScript, JavaScript, VB Script and other available web browser scripting languages to manipulate and transfer XML data from and to a web server using HTTP, bridging an independent connection channel between a webpage’s server side and client side.

What are the disadvantages of Ajax?

Following are the disadvantages of Ajax:

1. AJAX is dependent on Javascript. If there is some Javascript problem with the browser or in the OS, Ajax will not support
2. Ajax can be problematic in Search engines as it uses Javascript for most of its parts.
3. Source code written in AJAX is easily human readable. There will be some security issues in Ajax.
4. Debugging is difficult
5. Increases size of the requests
6. Slow and unreliable network connection.
7. Problem with browser back button when using AJAX enabled pages.

What are the advantages of Ajax?

Following are the advantages of Ajax:

* Bandwidth utilization – It saves memory when the data is fetched from the same page.
* More interactive
* Speeder retrieval of data

What is JSON in AJAX?

JSON stands for JavaScript Object Notation. It is easy to understand and data exchange is fast than XML. It supports array.

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 is the difference between JavaScript and AJAX?

JavaScript makes a request to the server and waits for the response. It consumes more bandwidth as it reloads the page.

AJAX sends a request to the server and doesn't wait for the response. It doesn't reload the page so consumes less bandwidth.

How to control the duration of an Ajax request?

AsyncPostBackTimeout property is used to control the duration of Ajax request. Deafult value of this property is 90 seconds.

Example –

<asp:ScriptManager runat="server" id="sample" AsyncPostBackTimeout="40"/>

Won’t my Server-aspect Framework provide me with Ajax?

You can be taking advantage of AJAX already. Many present Java-primarily based frameworks have already got a few degrees of AJAX interactions, and new frameworks and aspect libraries are being advanced to offer higher AJAX guidance. I may not list all of the Java frameworks that use AJAX right here, out of worry of lacking someone. However, you could discover a true listing at www.ajaxpatterns.org/Java_Ajax_Frameworks.

What is an asynchronous request in AJAX?

An Asynchronous request is defined as the script execution which allows proceeding with the next line of execution irrespective of the response from the web server after a request, which can be handled later upon the receipt of the response from the web server. Asynchronous is the most important mechanism in responding to the user without any delay where a user can still interact with the web pages irrespective of the responses from the server for the previous requests.

Is It Possible To Set Session Variables From Javascript?

It's not possible to set any session variables directly from javascript as it is purely a client side technology. You can use AJAX though to asynchronously...

What role of #&& in querystring?

# is treated as fragment delimiter to delimit the history state and && precedes is used to check on the information in the query string.

Does Ajax work with another language?

Absolutely. Java is a top-notch suit for AJAX! You can use Java Enterprise Edition servers to generate AJAX consumer pages and to serve incoming AJAX requests, manipulate server-aspect nations for AJAX customers, and join AJAX customers for your corporation resources. The JavaServer Faces aspect version is a top-notch suit for outlining and the use of AJAX additives.

What is AJAX event?

Ajax requests produce a wide variety of distinctive occasions that you can subscribe to. Here's a full listing of the activities and in what order they are triggered.

There are 2 types of events in Ajax
* Local Events: Local Events are callbacks that you can subscribe to inside the Ajax request object.

* Global Events: Global events are triggered on the document, calling any handlers who may be listening.

Won't My Server-side Framework Provide Me With Ajax?

You may be benefiting from AJAX already. Many existing Java based frameworks already have some level of AJAX interactions and new frameworks and component libraries are being developed to provide better AJAX support. I won't list all the Java frameworks that use AJAX here, out of fear of missing someone, but you can find a good list at www.ajaxpatterns.org/Java_Ajax_Frameworks.

If you have not chosen a framework yet it is recommended you consider using JavaServer Faces or a JavaServer Faces based framework. JavaServer Faces components can be created and used to abstract many of the details of generating JavaScript, AJAX interactions, and DHTML processing and thus enable simple AJAX used by JSF application developer and as plug-ins in JSF compatible IDE's, such as Sun Java Studio Creator.

Do I Really Need To Learn Javascript?

Basically yes if you plan to develop new AJAX functionality for your web application. On the other hand, JSF components and component libraries can abstract the details of JavaScript, DOM and CSS. These components can generate the necessary artifacts to make AJAX interactions possible. Visual tools such as Java Studio Creator may also use AJAX enabled JSF components to create applications, shielding the tool developer from many of the details of AJAX. If you plan to develop your own JSF components or wire the events of components together in a tool it is important that you have a basic understanding of JavaScript. There are client-side JavaScript libraries (discussed below) that you can call from your in page JavaScript that abstract browser differences. Object Hierarchy and Inheritance in JavaScript is a great resource for a Java developer to learn about JavaScript objects.

Does Ajax Work With Java?

Absolutely. Java is a great fit for AJAX! You can use Java Enterprise Edition servers to generate AJAX client pages and to serve incoming AJAX requests, manage server side state for AJAX clients, and connect AJAX clients to your enterprise resources. The JavaServer Faces component model is a great fit for defining and using AJAX components.

Do Ajax Applications Always Deliver A Better Experience Than Traditional Web Applications?

Not necessarily. Ajax gives interaction designers more flexibility. However, the more power we have, the more caution we must use in exercising it. We must be careful to use Ajax to enhance the user experience of our applications, not degrade it.

Where Should I Start?

Assuming the framework you are using does not suffice your use cases and you would like to develop your own AJAX components or functionality I suggest you start with the article Asynchronous JavaScript Technology and XML (AJAX) With Java 2 Platform, Enterprise Edition. If you would like to see a very basic example that includes source code you can check out the tech tip Using AJAX with Java Technology. For a more complete list of AJAX resources the Blueprints AJAX Home page.Next, I would recommend spending some time investigating AJAX libraries and frameworks. If you choose to write your own AJAX clients-side script you are much better off not re-inventing the wheel.

AJAX in Action by Dave Crane and Eric Pascarello with Darren James is good resource. This book is helpful for the Java developer in that in contains an appendix for learning JavaScript for the Java developer.

Are Ajax applications easier to develop than traditional Web Applications?

Not necessarily. Ajax programs necessarily contain walking complicated JavaScript code at the consumer. Making that complicated code green and bug-loose isn’t always a mission to be taken lightly, and higher improvement equipment and frameworks may be hard to assist us to meet that challenge.

How is Ajax different?

An Ajax utility removes the begin-forestall-begin-forestall nature of interplay at the Web by introducing an intermediary — an Ajax engine — between the person and the server. It looks like including a layer to the utility could make it much less responsive. However, the contrary is true.

The synchronous interplay sample of a conventional net utility (pinnacle) compares with the asynchronous sample of an Ajax utility (bottom).

Instead of loading a webpage, at the beginning of the consultation, the browser sends an Ajax engine — written in JavaScript and commonly tucked away in a hidden frame. This engine is accountable for each rendering of the interface the person sees and speaking with the server on the person’s behalf. The Ajax engine permits the person’s interplay with the utility to appear asynchronously — impartial of conversation with the server. So the person is by no means looking at a clean browser window and an hourglass icon, ready round for the server to do something.

What is a synchronous request in AJAX?

The synchronous and Asynchronous type requests in AJAX are used based on the request priority of the web server request. They should be carefully configured to make the server respond to the user based on the user requirement. The synchronous request waits for the server’s response after requesting to proceed with the next part of the script execution, which is crucial in a fast response mechanism. This should be avoided frequently to make the server highly responsive. Wherever the synchronous request mechanism is essential or inevitable, it should be used.

What are the different technologies used in AJAX?

AJAX involves different technologies such as HTML (and XHTML), CSS (for presentation layer), JSON, XML or XSLT (for data exchange between a web server and client), JavaScript and other APIs for asynchronous communication. AJAX is used for creating dynamic web pages. Examples of the websites that use AJAX are Google, Gmail, YouTube, Facebook etc. AJAX is a standard based on Internet Standards to comply with all the browsers and networks across the globe.

What Is Ajax?


AJAX (Asynchronous JavaScript and XML) is a newly coined term for two powerful browser features that have been around for years, but were overlooked by many web developers until recently when applications such as Gmail, Google Suggest, and Google Maps hit the streets.

Ajax isn’t a technology. It’s really several technologies, each flourishing in its own right, coming together in powerful new ways. Ajax incorporates:
* standards-based presentation using XHTML and CSS;
* dynamic display and interaction using the Document Object Model;
* data interchange and manipulation using XML and XSLT;
* Asynchronous data retrieval using XMLHttpRequest;
* JavaScript binding everything together.

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