Detailed explanation of jquery basic knowledge points
This time I will bring you a detailed explanation of the basic knowledge points of jquery. What are the precautions for using the basic knowledge points of jquery? The following is a practical case, let’s take a look.
jQuery is an excellent, lightweight js library that is compatible with CSS3 and various browsers (IE 6.0, FF1.5, Safari 2.0, Opera 9.0), and jQuery2.0 and subsequent This version will no longer support IE6/7/8 browsers. jQuery enables users to more easily process HTML (an application under Standard Universal Markup Language), events, implement animation effects, and easily provide AJAX interaction for websites. Another big advantage of jQuery is that its documentation is very complete, and various applications are also explained in detail, and there are many mature plug-ins to choose from.
1. The difference between jQuery entry function and Js entry function
[Note] js entry function refers to: window.onload = function (){};
Difference 1: Different writing numbers
The Js entry function can only appear once. If it appears multiple times, there will be an event coverage problem.
jQuery’s entry function can appear any number of times without event coverage.
Difference 2: Different execution timings
The Js entry function is executed after all file resources are loaded. These file resources include: page documents, external js files, external css files, pictures, etc.
The entry function of jQuery is executed after the document is loaded. The completion of document loading means: after the DOM tree is loaded, you can operate the DOM without waiting for all external resources to be loaded.
The order of document loading: from top to bottom, parsing and executing.
2. Mutual conversion between jQuery object and DOM object
①DOM object here refers to: using js The result returned by operating DOM
var btn = document.getElementById(“btnShow”); // btn就是一个DOM对象
②jQuery object here refers to: the result returned by using the method provided by jQuery to operate DOM
var $btn = $(“#btnShow”); // $btn就是一个jQuery对象
③DOM object converted into jQuery object
var $btn1 = $(btn); // 此时就把DOM对象btn转换成了jQuery对象$btn1 // $(document).ready(function(){}); // 调用入口函数 // 此处是将document这个js的DOM对象,转换成了jQuery对象,然后才能调用jQuery提供的方法:ready
④Convert jQuery object into DOM object
// 第一种方式 var btn1 = $btn[0]; // 此时就把jQuery对象$btn转换成了DOM对象btn1 (推荐使用此方式) // 第二种方式 var btn2 = $btn.get(0);// 此时就把jQuery对象$btn转换成了DOM对象btn2
3, jQuery selector
Description | Usage | |
Basic selector(Key points) | ||
#ID selector | $("#btnShow").css("color", "red");Select the one with the id btnShow Element (the return value is a jQuery object, the same below) | |
Class selector | $(“.liItem”).css(“color”, “red”);Select all elements containing class liItem | |
Tag selector | $(“li”).css(“color”, “red”);Select the tag name For all elements of li | |
Descendant selector | $(“#j_wrap li”).css(“color”, “red”);Select all descendant elements li of the element with id j_wrap |
|
Children selector | $(“#j_wrap > ul > li”).css(“ color", "red");Select all sub-elements ul of all sub-elements li of the element with id j_wrap | |
Selects an element with index number among the matched elements, and index is from Starting from 0 | $(“li:eq(2)”).css(“color”, ”red”); |
Select one of the li elements with index number 2 Element |
Select all elements with odd index numbers among the matched elements, and the index starts from 0 | $("li:odd").css("color", "red"); | Select all elements with odd index numbers in the li element |
:even | Select all elements with even index numbers among the matched elements, and the index starts from 0 | $("li:odd").css("color", "red"); Select all elements with even index numbers in the li element |
Filter selector (method) (Key point) | ||
find(selector) | Find all descendant elements of the specified element ( descendants) |
$(“#j_wrap”).find(“li”).css(“color”, “red”); Select the one with the id j_wrap All descendant elements li |
children() | Find the direct child elements (child elements) of the specified element |
$ ("#j_wrap").children("ul").css("color","red"); Select all child elements ul |
siblings() | Find all sibling elements (excluding self) |
$("#j_liItem").siblings().css("color" , “red”); Select all sibling elements with id j_liItem |
parent() | Find the parent element (parent ) |
$(“#j_liItem”).parent(“ul”).css(“color”,“red”); Select the parent element with id j_liItem |
eq(index) | Find the index element of the specified element, index is the index number, starting from 0 |
$("li").eq(2).css("color", "red"); Select the second one among all li elements |
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!
Recommended reading:
Detailed explanation of the overall architecture analysis and use of jquery
Detailed explanation of jQuery's method of judging the type and size of uploaded images
Detailed explanation of the use of jQuery framework
The above is the detailed content of Detailed explanation of jquery basic knowledge points. For more information, please follow other related articles on the PHP Chinese website!

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

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Windows operating system is one of the most popular operating systems in the world, and its new version Win11 has attracted much attention. In the Win11 system, obtaining administrator rights is an important operation. Administrator rights allow users to perform more operations and settings on the system. This article will introduce in detail how to obtain administrator permissions in Win11 system and how to effectively manage permissions. In the Win11 system, administrator rights are divided into two types: local administrator and domain administrator. A local administrator has full administrative rights to the local computer

Detailed explanation of division operation in OracleSQL In OracleSQL, division operation is a common and important mathematical operation, used to calculate the result of dividing two numbers. Division is often used in database queries, so understanding the division operation and its usage in OracleSQL is one of the essential skills for database developers. This article will discuss the relevant knowledge of division operations in OracleSQL in detail and provide specific code examples for readers' reference. 1. Division operation in OracleSQL

How to use PUT request method in jQuery? In jQuery, the method of sending a PUT request is similar to sending other types of requests, but you need to pay attention to some details and parameter settings. PUT requests are typically used to update resources, such as updating data in a database or updating files on the server. The following is a specific code example using the PUT request method in jQuery. First, make sure you include the jQuery library file, then you can send a PUT request via: $.ajax({u

The modulo operator (%) in PHP is used to obtain the remainder of the division of two numbers. In this article, we will discuss the role and usage of the modulo operator in detail, and provide specific code examples to help readers better understand. 1. The role of the modulo operator In mathematics, when we divide an integer by another integer, we get a quotient and a remainder. For example, when we divide 10 by 3, the quotient is 3 and the remainder is 1. The modulo operator is used to obtain this remainder. 2. Usage of the modulo operator In PHP, use the % symbol to represent the modulus

Title: jQuery Tips: Quickly modify the text of all a tags on the page In web development, we often need to modify and operate elements on the page. When using jQuery, sometimes you need to modify the text content of all a tags in the page at once, which can save time and energy. The following will introduce how to use jQuery to quickly modify the text of all a tags on the page, and give specific code examples. First, we need to introduce the jQuery library file and ensure that the following code is introduced into the page: <

Title: Use jQuery to modify the text content of all a tags. jQuery is a popular JavaScript library that is widely used to handle DOM operations. In web development, we often encounter the need to modify the text content of the link tag (a tag) on the page. This article will explain how to use jQuery to achieve this goal, and provide specific code examples. First, we need to introduce the jQuery library into the page. Add the following code in the HTML file:

How to tell if a jQuery element has a specific attribute? When using jQuery to operate DOM elements, you often encounter situations where you need to determine whether an element has a specific attribute. In this case, we can easily implement this function with the help of the methods provided by jQuery. The following will introduce two commonly used methods to determine whether a jQuery element has specific attributes, and attach specific code examples. Method 1: Use the attr() method and typeof operator // to determine whether the element has a specific attribute

jQuery is a popular JavaScript library that is widely used to handle DOM manipulation and event handling in web pages. In jQuery, the eq() method is used to select elements at a specified index position. The specific usage and application scenarios are as follows. In jQuery, the eq() method selects the element at a specified index position. Index positions start counting from 0, i.e. the index of the first element is 0, the index of the second element is 1, and so on. The syntax of the eq() method is as follows: $("s
