Exploring the hidden versions of Ajax: How many are you familiar with?

Ajax version reveals: What do you know?

Introduction:
In modern web development, Ajax technology is widely used, which can realize data interaction between web pages and servers without refreshing. However, you know what? Ajax is not a unified standard or specification, but a series of technology combinations. Let's take a look at Ajax and learn about its core version.

1. Early version of Ajax
1.0 version
The earliest version of Ajax was proposed by Jesse James Garrett in 2005 and has been widely used. The core technology used at that time included the combination of the XMLHttpRequest object and JavaScript. Through the XmlHttpRequest object, the web page can send a request through the backend server, receive the response data, and then use JavaScript to dynamically update the data to the web page.

Code sample:

var xmlhttp;
if (window.XMLHttpRequest) {
    // 创建新的XMLHttpRequest对象
    xmlhttp = new XMLHttpRequest();
} else {
    // 兼容旧版本的浏览器
    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
// 发送请求
xmlhttp.open("GET", "example.com", true);
xmlhttp.send(null);
// 接收响应
xmlhttp.onreadystatechange = function() {
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
        // 数据处理逻辑
    }
}

2. Updated version of Ajax
2.0 version
With the development of Web technology, Ajax has also undergone some updates and improvements. The most important one is the introduction of JSON (JavaScript Object Notation) data format in version 2.0. Compared with traditional XML format, JSON is more concise and easier to process. It is more suitable for the transmission and analysis of large-scale data, so it is widely used in version 2.0.

Code example:

var xmlhttp;
if (window.XMLHttpRequest) {
    xmlhttp = new XMLHttpRequest();
} else {
    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.open("GET", "example.com", true);
xmlhttp.send(null);
xmlhttp.onreadystatechange = function() {
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
        var response = JSON.parse(xmlhttp.responseText);
        // 数据处理逻辑
    }
}

Version 2.5
In version 2.5, the Ajax team took advantage of the new features of HTML5 to further improve the performance and functionality of Ajax. The most important update is the introduction of Web Sockets, which can achieve real-time two-way communication between the server and the client by establishing a persistent connection. This function is widely used in some instant messaging, games and other applications.

Code sample:

var socket = new WebSocket("ws://example.com");
socket.onopen = function() {
    // 连接成功
}
socket.onmessage = function(event) {
    var data = event.data;
    // 数据处理逻辑
}
socket.onclose = function() {
    // 连接关闭
}
socket.onerror = function(error) {
    console.log("WebSocket Error: " + error);
}

Summary:
Although Ajax is not a specific standard or specification, it provides a series of technologies that make Web development richer and more convenient. From the early version 1.0 to the current version 2.5, Ajax has been continuously updated and evolved, providing developers with more choices and tools. Through the introduction of this article, I believe you have a deeper understanding of the Ajax version, and I hope it will be helpful to you in your web development journey.

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