Ajax Programming

What is Ajax Programming?

Ajax stands for Asynchronous JavaScript and XML. It’s a programming technique, not a programming language.

AJAX is an advanced programming technique for creating faster, better and more interactive web applications with the help of HTML, CSS, XML, and JavaScript.

  • HTML: HTML stands for Hypertext Markup Language which is used to describe the structure of web applications.
  • CSS: CSS stands for Cascading Style Sheet used to provide styling and view web applications.
  • JavaScript: JavaScript is a scripting programming language used to make web applications interesting, user friendly and interactive.
  • XML: XML stands for Extensible Markup Language which is used to format and send or receive data from a web server.

The main function of AJAX is to update the content on your webpage asynchronously, which means that when a small portion of the content on the page needs to be changed, not the entire page is reloaded.

For example, you notice that when you click the Like button to like a post on Facebook, the whole page doesn’t load, only the button section is loaded.

Another common example of AJAX is Googles. When you enter any text into the Google’s search bar, you notice that Google automatically offers options in the search bar without manually refreshing the page.

Synchronous vs. Asynchronous:

Synchronous is a traditional loading technique that means that when a user sends a request to the server, the compiler waits until the server receives a response and not moves on to the next task.

But in Asynchronous technique, when the user sends a request to the server, the compiler does not wait for a response. It moves on to the next task, when the response is received it will return to it and show the output.

AJAX Open Standards:

Ajax is based on these open standards such as:

  • Browser based presentation using HTML and CSS.
  • The data is stored in XML format and brought through the server.
  • In the background, the XMLHttpRequest retrieves data in the browser.
  • JavaScript handles everything.

How Ajax Works?

AJAX uses a browser built in “XMLHttpRequest” object to request the data from the web server, and the HTML DOM is used to display or use the data in the web browser.

  1. The user sends the request through the user interface (UI) and the JavaScript request goes to the XMLHttpRequest object.
  2. The request is sent to the server via the XMLHttpRequest object.
  3. The server communicates with the database and retrieves data using backend programming languages such as PHP, ASP.net, Node, etc.
  4. The server returns JSON or XML data via the XMLHttpRequest callback function.
  5. Data is displayed on the browser using HTML and CSS.
  • XML HTTP Request Object: It’s an API in the form of an object whose methods are used to help send and receive data between web servers and web browsers.
  • Html DOM: DOM stands for Document Object Model. This is a programming API for XML and HTML documents. It explains the logical structure of a document and how it manipulates and accesses a document. When the browser is loaded, it creates a document object model of the page.

Properties of XML HTTP Request Object:

  • readystate:

“readystate” is the property of XML HTTP Request Object that grasp the status of the XML HTTP Request.

  • 0: It means request not initialized yet.
    • 1: It means that the server connection is successfully established.
    • 2: It means that request received to the server.
    • 3: It means that the request is in processing state.
    • 4: It means that the request is processed successfully and response is ready to use.
  • onreadystatechange:

“onreadystatechange” is the property of the XML HTTP Request Object which means that the function is to call when ready state property changes.

  • status:

“status” is the property of the XML HTTP request object that gives us the status number of that particular request

  • 200: It means that the status is OK.
  • 403: It means that the page is forbidden.
  • 404: It means that the page is not found.

Methods of XML HTTP Request Object:

To send the request to the server XML HTTP Request Object gives us two methods

  • Open()
  • Send()

Xhttp.open(“GET”,  “info.txt” ,  true);

Xhttp.send();

Bottom Line:

Ajax is a programming technique that allows us to create better and advance ways to interact with web pages.

It also makes our web pages faster than before and update the content on the web pages asynchronously.

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See Also
What is Database Management System
HTML Basic Elements