


jquery's method of obtaining objects is sufficient to handle various common types of objects_jquery
$("*")
Get all objects
$("#element")
Get the id as element The object is equivalent to document.getElementById("element");
$(".abc")
Get the object with class abc
$("div")
Get all div elements in html
$("#a,.b,p")
Get id a and class b and all p elements
$("# a .b p")
Get the p element under the element with id a and class b
(2) Get the hierarchical object
$("div> input")
Get all input objects under div
$("div h")
Get an h element immediately after the div
$("div~p ")
Get all p elements after the element div
(3) Simple object acquisition
$("element:first")
Get The first element of an element on the page, such as $("div:frist"), represents the first div
$("element:last")
Gets the last element of an element on the page, such as $("div:frist") represents the last div
$("element:not(selector)")
Remove all elements matching the selector such as $("input:not(:check )") represents all unchecked checkboxes
$("element:even")
Gets the even rows of element elements
$("element:odd")
Get the odd row of elements
$("element:eq(index)")
Get the element with a specific index such as $("div:el(2)") for the third div
$("element:gt(index)")
Matches all elements greater than the given index value
$("element:lt(index)")
Matches all Elements less than the given index
$(":header")
Matches h-tagged elements
$("element:animated")
Matches all elements that do not perform animation effects Elements of
(4) Acquisition of content objects and visibility of objects
$("Element:contains(text)")
Text in elements Whether it contains a certain letter or string
$("Element:empty")
Get an element object that does not contain text or sub-elements
$("Element:parent")
Get the object element containing text or sub-elements
$("Element:has(selector)")
Match whether a certain element contains a certain element such as $("p:has(span) ") means all p elements containing span elements
$("Element:hidden")
matches all invisible elements, including display:none and elements whose input attribute is hidden
$("Element:visible")
Match all courseware elements
(5) Advanced object acquisition
$("Element[id]")
Get all elements with id attribute
$("Element[attribute=abcd]")
Get all elements with an attribute of abcd
$("Element [attribute!=abcd]")
Get all elements whose attribute is not abcd
$("Element[attribute^=ab]")
Get all elements whose attribute starts with ab The elements of
$("Element[attribute$=ab]")
Get all the elements with an attribute ending in ab
$("Element[attribute*=ab]" )
Get all elements with an attribute containing ab
$("Element[selector1][selector2][...]")
Conform to attribute selectors such as $(" input[id][name][value=abcd]") means to obtain the input element with ID, Name and value abcd
(6) Obtaining sub-elements
$("Element:nth-child(index)")
Select the Nth child element under the parent, the index starts from 1
:nth-child(even) even
:nth- child(odd) odd number
:nth-child(3n) expression
:nth-child(2) index
:nth-child(3n 1) expression
$(" Element:first-child")
The first child element under the parent
$("Element:last-child")
The last child element under the parent
$("Element:only-child")
The only child element under the parent
(7) Obtaining the form object
$(:input)
Can only match the input element type input button select textarea
$(:text)
All current line text boxes
$(:password)
All password boxes
$(:radio)
All radio buttons
$(:checkbox)
All checkboxes
$( :submit)
All submission buttons
$(:image)
All image fields
$(:reset)
All recharge buttons
$(:button )
All buttons
$(:file)
All file upload fields
$(:hidden)
All invisible elements or elements of type hidden
$(:enabled)
All available input elements
$(:disabled)
All disableable input elements
$(:checked)
All checkbox elements
$(:selected)
All drop-down tables
(8) Setting and removing element attributes
$("Element").attr(name)
Get the attribute value of the first matching element such as $("img").attr("src");
$("Element") .attr({key:value,key:value,...})
Set multiple attributes for an element at once
$("Element").attr(key, value)
Set an attribute for an element
$("Element").attr(key,function)
Set a calculated attribute for all matching elements
$ ("Element").removeAttr(name)
Remove an attribute

The main difference between Python and JavaScript is the type system and application scenarios. 1. Python uses dynamic types, suitable for scientific computing and data analysis. 2. JavaScript adopts weak types and is widely used in front-end and full-stack development. The two have their own advantages in asynchronous programming and performance optimization, and should be decided according to project requirements when choosing.

Whether to choose Python or JavaScript depends on the project type: 1) Choose Python for data science and automation tasks; 2) Choose JavaScript for front-end and full-stack development. Python is favored for its powerful library in data processing and automation, while JavaScript is indispensable for its advantages in web interaction and full-stack development.

Python and JavaScript each have their own advantages, and the choice depends on project needs and personal preferences. 1. Python is easy to learn, with concise syntax, suitable for data science and back-end development, but has a slow execution speed. 2. JavaScript is everywhere in front-end development and has strong asynchronous programming capabilities. Node.js makes it suitable for full-stack development, but the syntax may be complex and error-prone.

JavaScriptisnotbuiltonCorC ;it'saninterpretedlanguagethatrunsonenginesoftenwritteninC .1)JavaScriptwasdesignedasalightweight,interpretedlanguageforwebbrowsers.2)EnginesevolvedfromsimpleinterpreterstoJITcompilers,typicallyinC ,improvingperformance.

JavaScript can be used for front-end and back-end development. The front-end enhances the user experience through DOM operations, and the back-end handles server tasks through Node.js. 1. Front-end example: Change the content of the web page text. 2. Backend example: Create a Node.js server.

Choosing Python or JavaScript should be based on career development, learning curve and ecosystem: 1) Career development: Python is suitable for data science and back-end development, while JavaScript is suitable for front-end and full-stack development. 2) Learning curve: Python syntax is concise and suitable for beginners; JavaScript syntax is flexible. 3) Ecosystem: Python has rich scientific computing libraries, and JavaScript has a powerful front-end framework.

The power of the JavaScript framework lies in simplifying development, improving user experience and application performance. When choosing a framework, consider: 1. Project size and complexity, 2. Team experience, 3. Ecosystem and community support.

Introduction I know you may find it strange, what exactly does JavaScript, C and browser have to do? They seem to be unrelated, but in fact, they play a very important role in modern web development. Today we will discuss the close connection between these three. Through this article, you will learn how JavaScript runs in the browser, the role of C in the browser engine, and how they work together to drive rendering and interaction of web pages. We all know the relationship between JavaScript and browser. JavaScript is the core language of front-end development. It runs directly in the browser, making web pages vivid and interesting. Have you ever wondered why JavaScr


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