Commonly used CSS3 basic selectors include: 1. Wildcard selector "*"; 2. Class selector ".class name"; 3. Element selector; 4. ID selector "#id name" ; 5. The group selector "E, F,..." can group elements with the same style together. Use a comma "," to separate each selector.
The operating environment of this tutorial: Windows 7 system, CSS3&&HTML5 version, Dell G3 computer.
5 common basic selectors in css3
1. Wildcard selector (supported by all browsers)
The general selector is represented by *, which is used to select all elements, or all elements under a certain element;
*{marigin: 0;
padding: 0;
font-size: 14px;
}You must have seen the above code in the reset style file a lot, and what it represents Yes, the margin and padding of all elements are set to 0, and the font size is set to 14px. The other way is to select all elements under a certain element:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>通配符选择器</title>
<style>
.demo * {
width: 50px;
height: 50px;
border: 1px solid blue;
margin: 10px;
}
</style>
</head>
<body>
<div class="demo">
<div>1</div>
<p>2</p>
<span>3</span>
</div>
</body>
</html>Rendering:
We can see that the three sub-elements div, p, and span in the demo element do not have CSS styles set respectively, but as long as we set a unified style for all elements under the demo element, then Styles will appear on the three sub-elements div, p, and span in the demo element.
2. Class selector (All browsers support class selectors, but multi-class selectors (.className1.className2) are not supported by ie6.)
The class selector selects based on the class name, preceded by ".", which specifies the style in a way that is independent of the document element. Before using the class selector, you need to define the class name on the html element. In other words, you need to ensure that the class The name exists in the html tag.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>类选择器</title>
<style>
.demo {
width: 200px;
height: 200px;
margin: 50px auto;
background: #2DC4CB;
}
</style>
</head>
<body>
<div class="demo">类选择器</div>
</body>
</html>Rendering:
3. Element selector (supported by all browsers)
Element selection (tag name selector) is the most common and basic selector among CSS3 selectors. The element selector is actually the element of the document, such as html, body, p, p, etc. In the following example, the span element is selected and the font color is set to red.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>元素选择器</title>
<style>
.demo {
width: 200px;
height: 200px;
margin: 50px auto;
}
span {
color: red;
}
</style>
</head>
<body>
<div class="demo">
<p>这里使用<span>元素选择器</span>改变了样式</p>
</div>
</body>
</html>Rendering:
4.ID selector (all browsers support)
ID The selector is very similar to the class selector mentioned above. Before using the ID selector, you need to add the ID name to the html document so that the corresponding element can be found in the style selector. The difference is ID selection. The selector is the only value in a page. When using a class, we add a "." sign (.className) before the corresponding class name, and the id selector uses "#" before the name, such as (#demo).
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>ID选择器</title>
<style>
#demo {
width: 200px;
height: 200px;
margin: 50px auto;
background: #FF0000;
}
</style>
</head>
<body>
<div id="demo">ID选择器</div>
</body>
</html>Rendering:
There are several places where the ID selector needs special attention:
First: one id in a document The selector is only allowed to be used once, because the id is unique in the page;
Second, id selectors cannot be combined and used like class selectors, and an element can only be named with one id name;
Third, you can use the same id name in different documents. For example, you can define "#important" for h1 in "test.html", or you can define p for "test1.html". The id is "#important", but the premise is that only one id called "#important" is allowed in test.html or test1.html.
5. Group selector (supported by all browsers)
When several elements have the same style attributes, they can call a statement together, and use Comma separated. Group selectors group elements with the same style together. Each selector is separated by a comma ",". This comma tells the browser that the rule contains multiple different selectors. If there is no comma, , then the meaning expressed is completely different. Omitting the comma becomes the descendant selector we mentioned earlier. You must be careful about this when using it.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>群组选择器</title>
<style>
.demo {
width: 200px;
height: 200px;
margin: 50px auto;
background: #FF0000;
}
p,
li {
color: blue;
}
.demo1,
.demo2 {
color: #fff;
}
</style>
</head>
<body>
<div class="demo">
<p>这里是一个段落!</p>
<ul>
<li>列表</li>
</ul>
<a href="#" class="demo1">链接一</a><br>
<span class="demo2">文字文字！</span>
</div>
</body>
</html>Rendering:
(Learning video sharing: css video tutorial)
The above is the detailed content of What are the commonly used CSS3 basic selectors?. For more information, please follow other related articles on the PHP Chinese website!
What are the limitations of React?May 02, 2025 am 12:26 AMReact'slimitationsinclude:1)asteeplearningcurveduetoitsvastecosystem,2)SEOchallengeswithclient-siderendering,3)potentialperformanceissuesinlargeapplications,4)complexstatemanagementasappsgrow,and5)theneedtokeepupwithitsrapidevolution.Thesefactorsshou
React's Learning Curve: Challenges for New DevelopersMay 02, 2025 am 12:24 AMReactischallengingforbeginnersduetoitssteeplearningcurveandparadigmshifttocomponent-basedarchitecture.1)Startwithofficialdocumentationforasolidfoundation.2)UnderstandJSXandhowtoembedJavaScriptwithinit.3)Learntousefunctionalcomponentswithhooksforstate
Generating Stable and Unique Keys for Dynamic Lists in ReactMay 02, 2025 am 12:22 AMThecorechallengeingeneratingstableanduniquekeysfordynamiclistsinReactisensuringconsistentidentifiersacrossre-rendersforefficientDOMupdates.1)Usenaturalkeyswhenpossible,astheyarereliableifuniqueandstable.2)Generatesynthetickeysbasedonmultipleattribute
JavaScript Fatigue: Staying Current with React and Its ToolsMay 02, 2025 am 12:19 AMJavaScriptfatigueinReactismanageablewithstrategieslikejust-in-timelearningandcuratedinformationsources.1)Learnwhatyouneedwhenyouneedit,focusingonprojectrelevance.2)FollowkeyblogsliketheofficialReactblogandengagewithcommunitieslikeReactifluxonDiscordt
Testing Components That Use the useState() HookMay 02, 2025 am 12:13 AMTotestReactcomponentsusingtheuseStatehook,useJestandReactTestingLibrarytosimulateinteractionsandverifystatechangesintheUI.1)Renderthecomponentandcheckinitialstate.2)Simulateuserinteractionslikeclicksorformsubmissions.3)Verifytheupdatedstatereflectsin
Keys in React: A Deep Dive into Performance Optimization TechniquesMay 01, 2025 am 12:25 AMKeysinReactarecrucialforoptimizingperformancebyaidinginefficientlistupdates.1)Usekeystoidentifyandtracklistelements.2)Avoidusingarrayindicesaskeystopreventperformanceissues.3)Choosestableidentifierslikeitem.idtomaintaincomponentstateandimproveperform
What are keys in React?May 01, 2025 am 12:25 AMReactkeysareuniqueidentifiersusedwhenrenderingliststoimprovereconciliationefficiency.1)TheyhelpReacttrackchangesinlistitems,2)usingstableanduniqueidentifierslikeitemIDsisrecommended,3)avoidusingarrayindicesaskeystopreventissueswithreordering,and4)ens
The Importance of Unique Keys in React: Avoiding Common PitfallsMay 01, 2025 am 12:19 AMUniquekeysarecrucialinReactforoptimizingrenderingandmaintainingcomponentstateintegrity.1)Useanaturaluniqueidentifierfromyourdataifavailable.2)Ifnonaturalidentifierexists,generateauniquekeyusingalibrarylikeuuid.3)Avoidusingarrayindicesaskeys,especiall
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
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.
ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment
SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.
PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool
MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
