3-point summary of Ajax technical principles_AJAX related
This article mainly introduces a 3-point summary of the technical principles of Ajax. Friends in need can refer to
ajax: Asynchronous Javascript and XML Asynchronous Javascript and XML.
is a web development technology for creating interactive web applications.
1.0 Advantages:
1.1 Improved user experience through asynchronous mode.
1.2 Optimizes the transmission between the browser and the server, reducing unnecessary data round-trips and bandwidth usage.
1.3 The Ajax engine runs on the client side and takes on part of the grouping that was originally borne by the server, thus reducing the server load under a large number of users.
2.0 Working Principle
The core of Ajax is the Javascript object XmlHttpRequest. This object was first referenced in IE5 and is a technology that supports asynchronous requests. XmlHttpRequest allows you to use Javascript to make requests to the server and process the response, rather than blocking the user, achieving a refresh-free effect.
Due to differences between browsers, there are also differences in the way to create XmlHttpRequest objects (mainly differences between IE and other browsers).
2.1 A more general method of creating asynchronous requests:
function CreateXmlHttp() { //非IE浏览器创建XmlHttpRequest对象的方法 if (window.XmlHttpRequest) { xmlhttp = new XmlHttpRequest(); } //IE浏览器创建XmlHttpRequest对象的方法 if (window.ActiveXObject) { try { xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { try { xmlhttp = new ActiveXObject("msxml2.XMLHTTP"); } catch (ex) { } } } }
2.2 XmlHttpRequest related attributes:
onreadystatechange The event handler for the event triggered each time the state changes.
responseText The string form of the data returned from the server process.
responseXML DOM-compatible document data object returned from the server process.
Status Text The string information accompanying the status code
ReadyState Object status value
0 (not initialization) Object has been established, but it has not been initialized (the open method has not yet been called)
1 (initialization) Object has been established, and the Send method has not yet been called
# 2 (Send data) The send method has been called, but the current status and http header are unknown
3 (Data is being transmitted) Part of the data has been received because the response and http header are incomplete. At this time, it is obtained through responseBody and responseText Some data will have errors,
4 (Complete) The data reception is completed. At this time, the complete response data can be obtained through responseXml and responseText
2.3 Simple Demo example:
function SendAsyncRequest() { var data = document.getElementById("XXId").value; CreateXmlHttp(); //创建XmlHttpRequest对象 if (!xmlhttp) { //判断对象是否创建成功 alert("创建xmlhttp对象异常!"); return false; } xmlhttp.open("POST", url, false); //开始发送异步请求 xmlhttp.onreadystatechange = function () { if (xmlhttp.readyState == 4 && xmlhttp.status == 200 ) { document.getElementById("XXShowId").innerHTML = xmlhttp.ResponseText; //数据接收完毕 } } xmlhttp.send(); }
3.0 Disadvantages:
1. It destroys the normal behavior of the browser's back button. After dynamically updating the page, it is impossible to return to the state of the previous page.
2. Using Javascript as the basic engine of Ajax, the compatibility of Javascript is not very good. (Of course, the popular JavaScript libraries such as Jquery have greatly improved these problems, and the call to Ajax is also much more convenient. This article only briefly describes the basic implementation principles of Ajax).
The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
Related articles:
AJAX encapsulated class usage guideAJAX beginner tutorial: First introduction to AJAXDetailed explanation of browser and server interaction in AjaxThe above is the detailed content of 3-point summary of Ajax technical principles_AJAX related. For more information, please follow other related articles on the PHP Chinese website!

Node.js excels at efficient I/O, largely thanks to streams. Streams process data incrementally, avoiding memory overload—ideal for large files, network tasks, and real-time applications. Combining streams with TypeScript's type safety creates a powe

The differences in performance and efficiency between Python and JavaScript are mainly reflected in: 1) As an interpreted language, Python runs slowly but has high development efficiency and is suitable for rapid prototype development; 2) JavaScript is limited to single thread in the browser, but multi-threading and asynchronous I/O can be used to improve performance in Node.js, and both have advantages in actual projects.

JavaScript originated in 1995 and was created by Brandon Ike, and realized the language into C. 1.C language provides high performance and system-level programming capabilities for JavaScript. 2. JavaScript's memory management and performance optimization rely on C language. 3. The cross-platform feature of C language helps JavaScript run efficiently on different operating systems.

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

SublimeText3 Chinese version
Chinese version, very easy to use

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

WebStorm Mac version
Useful JavaScript development tools

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool
