#id
返回值
Element
参数
id (String) : 用于搜索的,通过元素的 id 属性中给定的值
示例
查找 ID 为"myDiv"的元素。
HTML 代码:
id="notMe"
jQuery 代码:
结果:
---------------------------------------------------------------------------------------
element
返回值
Array
参数
element (String) : 一个用于搜索的元素。指向 DOM 节点的标签名。
示例
查找一个 DIV 元素。
HTML 代码:
SPAN
jQuery 代码:
结果:
.class
返回值
Array
参数
class (String) : 一个用以搜索的类。一个元素可以有多个类,只要有一个符合就能被匹配到。
示例
查找所有类是 "myClass" 的元素.
HTML 代码:
span class="myClass"
jQuery 代码:
结果:
---------------------------------------------------------------------------------------
*
返回值
Array
示例
找到每一个元素
HTML 代码:
SPAN
P
jQuery 代码:
结果:
P
]---------------------------------------------------------------------------------------
selector1,selector2,selectorN
返回值
Array
参数
selector1 (Selector) : 一个有效的选择器
selector2 (Selector) : 另一个有效的选择器
selectorN (Selector) : (可选) 任意多个有效选择器
示例
找到匹配任意一个类的元素。
HTML 代码:
p class="myClass"
span
p class="notMyClass"
jQuery 代码:
结果:
p class="myClass"
, span ]ancestor descendant
返回值
Array
参数
ancestor (Selector) : 任何有效选择器
descendant (Selector) : 用以匹配元素的选择器,并且它是第一个选择器的后代元素
示例
找到表单中所有的 input 元素
HTML 代码:
jQuery 代码:
结果:
---------------------------------------------------------------------------------------
parent > child
返回值
Array
参数
parent (Selector) : 任何有效选择器
child (Selector) : 用以匹配元素的选择器,并且它是第一个选择器的子元素
示例
匹配表单中所有的子级input元素。
HTML 代码:
jQuery 代码:
结果:
---------------------------------------------------------------------------------------
prev + next
Return value
Array
Parameters
prev (Selector) : any valid selector
next (Selector): A valid selector immediately following the first selector
Example
Matches all input elements following label
HTML code:
$("label input")
Result:[ , ] ---------------- -------------------------------------------------- --------------------------
Match all sibling elements after the prev element
Matches all sibling elements after the "prev" element that match the filtering "siblings" selector.
Parameters
prev(Selector) : any valid selector
siblings (Selector) : a selector that acts as a sibling of the first selector
Example Find all input elements that are siblings of the form
HTML code:
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.

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.


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