Web development has become the most common job for various enterprises of multiple disciplines. These web applications require different application development technologies to create asynchronous web applications. AJAX is one such technique that helps to build faster, robust, and interactive web applications. In this article, we have compiled a list of basic and advanced AJAX interview questions discussing the basics, its features, and various components.
The various advantages of AJAX are:
Some real-life projects and web applications that use AJAX are:
The important methods of XMLHttpRequest are:
It is the process of fetching data from the server to receive near-live data regularly.
There are a few limitations that AJAX users should keep in mind. These are:
AJAX is an abbreviation of the initials of different technologies. They are:
XMLHttpRequest has various tasks when applied with AJAX. These are:
AJAX creates HTTP requests with the help of XMLHttpRequest. It promotes transferring data between the client and the server, which is the request and response selection. Developers can perform the same operation and fetch data from URL without a page refresh through AJAX. There are three steps for doing this:
As with any technology, there are several issues that developers face. Two key security issues associated with the AJAX are:
There are 2 methods that helps in transferring data between multiple security domains.
AJAX works smoothly with various other programming languages. AJAX is client-side so it really does not matter how the remote service/API is built. AJAX just needs to remotely connect to the service to fetch/send data.
Five different ready states are there in an AJAX request. These are:
There are different situations where developers can use AJAX.
In AJAX, the callback functions aid in handling responses from the server. Such functions can either be a named function (that developers use frequently) or an anonymous function. Developers can implement a broad spectrum of AJAX tasks on a website by simply creating a function that does the XMLHttpRequest execution along with a callback function, which accomplishes each AJAX task.
Some popular tools that help developers debug any AJAX-based website and apps are:
Some well-known web browsers that support AJAX are Google Chrome, Opera, Mozilla Firefox, Microsoft Edge and Safari.
Some well-known AJAX enabled/enabler frameworks are:
While retrieving data, the AJAX request must use the HTTP GET request. It is because the data won't alter for a presented request URL. One should use the HTTP POST when the state requires an update on the server.
The term "Asynchronous" means that a wide variety of events can occur independently of one another using AJAX. As soon as the client-side initializes an AJAX-based callback to the server, the client won't have to wait for any response. The application will continue to use the web application while processing the request.
Names of some protocols used by AJAX are:
We cannot leverage the functionalities of AJAX if -
Developers use AJAX to perform callbacks. These callbacks are actions (functions) that are executed when an asynchronous task completes and is used to handle the outcome. This callback process takes a round trip to and from the server without posting the complete page to the server. Thus, this technique helps AJAX interact with the server without a page refresh. By not performing a total postback and sending all form-related data to the server, the AJAX callback helps in reducing network utilization.
There are 2 different ways of handling encoding in AJAX. These are:
We can create AJAX objects by using the following syntax:
var ajax= New ajaxObject('page path')
Here the 'page path' is the URL used for the object to call. The URL must be of the same domain as the webpage.
AJAX provides the ability to update a page dynamically through AJAX interaction. That may result in a drastic change in the form, appearance, or even the state of a web page. Using the back & forward button, navigating through an AJAX-based page, or printing the page directly from the browser can create issues. So, while designing and developing an AJAX-based application, developers should consider that the expected behavior the page may reflect in case of navigation.
Cross-domain calling renders the ability to automatically and concurrently access or change data among two or more varied security domains.
Ajax does not cater to built-in multimedia functions. It is not so supportive of in-built applications. But it can use other browser functionalities and plugins such as QuickTime, SVG, and Flash. Developers can achieve AJAX-based general multimedia functions through mashup and hack.
Yes, it is possible to send an image using AJAX.
AJAX requests by default, issue all requests. But browsers may send responses with the help of cache. For preventing such a scenario, developers can set the cache to false. We can apply this concept to prevent caching of all future AJAX requests, irrespective of jQuery method used.
The response time, also known as latency, is the time spread that passes from the commencement of a client-based request processing to the server until its ends. When the time duration is longer than the expected time or regular time, it is called delay.
Text hints and auto-complete textboxes are two widespread uses of AJAX. When the user on the client-side types a couple of letters, a listing of all values that begin with these typed letters appears below as recommendations. Behind this operation, the application makes a callback to a web service. This web service then fetches all values that start with these characters.
For improving performance of AJAX, we can go through the following steps:
We can send multiple text values through any response text with the help of a concatenation operator (|). By splitting the text data into various segments using the pipe operator like this: responseText.split(‘|’). It renders an array of text that developers can send through JSQN in an array format. In other words, if the response is text, we can stringified array that can be parsed in client-side.