AJAX and HTTP Overview

HTTP (Hypertext Transfer Protocol) is a fundamental protocol for transferring data over the World Wide Web. It allows clients (like web browsers) to communicate with servers and retrieve information, such as web pages, images, and videos.

When you visit a website, your browser sends a request to the server. The server processes this request, finds the requested information, and sends back a response. This completes the communication.

HTTP is stateless, meaning each request is treated independently; the server doesn't remember previous interactions. This means every request must include all necessary information.

Long polling is a technique where a client keeps a connection open to the server, waiting for an update. The server sends data as soon as it becomes available, resulting in more efficient communication.

Traditional web browsers use short polling, which means they repeatedly send requests to check for updates even if there's no new information. This can be inefficient, especially with slow connections.

Rendering refers to the process where a web browser transforms the raw code and data from a server into a visually presentable web page that you see on your screen.

Long polling can be more efficient than traditional short polling, as it avoids repeatedly sending requests when no new data exists. It allows for the server to push updates to the client as soon as they become available, rather than relying on the client to repeatedly check.

Due to its stateless nature, HTTP doesn't inherently provide a way to keep track of previous client interactions. Each request needs to include all the necessary information, regardless of prior requests.

AJAX stands for Asynchronous JavaScript and XML. It is used to update web pages dynamically without reloading the entire page.

XMLHttpRequest (XHR) is a JavaScript object that lets your web page communicate with a server to get data in formats like XML, JSON, HTML, or plain text. It's the heart of AJAX.

In synchronous communication, JavaScript waits for the server response before continuing. In asynchronous communication, JavaScript keeps running even while waiting for a server response, making the website feel more responsive.

AJAX can make web pages appear faster by loading only the specific parts that need updating, instead of reloading the whole page.

AJAX can be used to create more interactive web experiences. For example, you can instantly autocomplete search suggestions as you type or view updated data in real-time without refreshing the page.

The open() method establishes the connection with a server. The URL specifies where the request is sent, and Method specifies the HTTP method used (GET, POST, etc.). The async parameter determines whether the request is asynchronous or synchronous.

The send() method sends the request to the server. With the GET method, parameters are included in the URL. With the POST method, variables are sent as part of the request.

It's a process where the server receives the request and processes it before sending a response back to the client. This response can include data in various formats, such as JSON or HTML.

The readyState property of the XMLHttpRequest object represents the state of the request. It takes values between 0 and 4, indicating different stages in the communication with the server.

The onreadystatechange property defines a function that is executed whenever the readyState of the XMLHttpRequest object changes.

This property provides the HTTP status code sent by the server in response to the request. Common values are 200 for successful requests and 404 for "not found".

This property contains the textual response received from the server after a successful request.

This property contains the response received from the server in the XML format.