This article is the official HTML5 training tutorial of H5EDU organization. It mainly introduces: JavaScript enhancement tutorial - Get content and attributes
jQuery - Get content and attributes
jQuery has powerful methods to manipulate HTML elements and attributes.
jQuery DOM operation
A very important part of jQuery is the ability to operate DOM.
jQuery provides a series of DOM-related methods that make it easy to access and manipulate elements and attributes.
lamp DOM = Document Object Model
DOM defines standards for accessing HTML and XML documents:
"The W3C Document Object Model is a platform- and language-independent interface that allows programs and scripts to dynamically access and update the content of documents. Structure and style. "
Get content - text(), html() and val()
Three simple and practical jQuery methods for DOM manipulation:
text() - Set or return the text content of the selected element
html() - Sets or returns the content of the selected element (including HTML tags)
val() - Sets or returns the value of a form field
The following example demonstrates how to obtain content through the jQuery text() and html() methods:
Example
$("#btn1").click(function(){
alert("Text: " + $("#test").text());
});
$("#btn2"). click(function(){
alert("HTML: " + $("#test").html());
});
The following example demonstrates how to get the value of an input field through the jQuery val() method:
Example
$("#btn1").click(function(){
alert("The value is: " + $("#test").val());
});
Get attributes - attr( )
jQuery attr() method is used to get the attribute value.
The following example demonstrates how to get the value of the href attribute in the link:
Example
$("button").click(function(){
alert($("#runoob").attr("href"));
});

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.

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.


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