Detailed explanation of usage in jquery

jQuery is one of the most widely used JavaScript libraries and has now become one of the essential skills for front-end development. This article will introduce the usage of jQuery library in detail, aiming to help readers better grasp the basic concepts, syntax and common methods of jQuery.

1. Introduction to jQuery

jQuery is a fast and concise JavaScript library that encapsulates the core features of JavaScript. It provides an easy-to-use API that simplifies HTML document traversal, event handling, animation effects, AJAX interaction and other operations, allowing developers to write Web applications more efficiently.

Let’s see how to use jQuery in a web application.

2. Introduce jQuery

To use jQuery, we need to introduce it into the web application. There are two ways to introduce jQuery:

1. Download the jQuery file (recommended)

We can download the jQuery file on the jQuery official website, and then introduce it in the HTML page as follows :

<script src="jquery.js"></script>

Introduce the above code before the </head> tag to introduce the jQuery library into the web page. Note that the file name can vary depending on the version you downloaded.

2. Introducing jQuery through CDN

Another way to introduce jQuery is to use a CDN (Content Delivery Network). You only need to introduce it in the HTML page as follows:

<script src="https://cdn.jsdelivr.net/jquery/3.5.0/jquery.min.js"></script>

This allows you to pull in the latest version of jQuery files from the CDN without having to download and maintain the file yourself.

3. jQuery syntax

All functions in the jQuery library are implemented through the jQuery() function. This function is also known as the $ function, and you can pass a selector to it to get the jQuery object of the specified element, like this:

$(selector).action()

• $ Symbol definition jQuery
• selector is the HTML element to be operated
• action() is the action to be performed, such as addClass(), fadeOut (), animate(), etc.

4. jQuery selector

jQuery selector allows us to select the DOM based on the element's tag name, class, attribute and attribute value. element. Unlike traditional JavaScript DOM selectors, jQuery selectors are not case-sensitive.

Here are some common jQuery selectors:

Selector	Description
*	Select all elements
#id	Select Element with the specified id
.class	Select the element with the specified class
element	Select all elements of the specified element type
element.class	Select the specified element class Elements whose attributes contain the specified value
element,element	Select all elements of the specified element type that are of the specified element type
:first	Select the first specified element in the document
:last	Select the last specified element in the document
:even	Select all even-numbered elements in the document
:odd	Select all specified elements at odd positions in the document
:eq(index)	Select the specified element at the specified position (starting from the 0th one)
:gt(no)	Select the specified element after the specified position
:lt(no)	Select the specified element before the specified position
:header	Select all header elements (h1 ~ h6)
: not(selector)	Select elements that do not match the specified selector
:contains(text)	Selects elements that contain the specified text
:empty	Selects elements that do not contain child elements and text
:hidden	Select all hidden elements
:visible	Select all Visible elements

5. jQuery events

jQuery events are the most convenient way for us to operate HTML elements. Here are some common jQuery events:

##EventDescriptionMouse click eventMouse double click eventMouse enter eventMouse out eventMouse button pressed eventRelease mouse button eventPress Keyboard button eventRelease keyboard button eventElement gets focus eventElement loses focus eventSubmit form eventLoad page eventResize page eventPage scroll eventElement content change event

click()
dblclick()
mouseenter()
mouseleave()
mousedown()
mouseup()
keydown()
keyup()
focus()
blur()
submit()
load()
resize()
scroll()
change()

6. jQuery effects

jQuery provides a set of powerful effect methods that allow us to easily add animation effects, change element content, element position, Element size etc. Here are some common jQuery effects:

##Effect ##hide()show()toggle()fadeIn()fadeOut()fadeToggle()##slideDown ()slideUp()slideToggle()Create custom animationStop animationMove the scroll bar up to the top of the specified elementMove the scroll bar to the left to the left of the specified elementGet the specified CSS property The valueSet the value of the CSS propertyGet the width of the elementGet the height of the element##7. jQuery AJAXAJAX is an asynchronous JavaScript and XML technology that allows us to use HTTP request and response data through JavaScript without reloading the entire The page can update part of the page. jQuery provides a set of powerful AJAX methods that allow us to use AJAX technology easily. Here are some common jQuery AJAX methods:

Description
Hide the specified element
Show the specified element
Hide the state of the displayed element
Fade in the specified element, based on transparency
Fade out the specified element, based on transparency
Hide the state of the displayed element, based on transparency
Slide down to display the specified element
Slide up to hide the specified element Element
Expand or shrink element	##animate()
	stop()
	scrollTop()
	scrollLeft()
	css(property)
	css(property, value)
	width()
	height()

AJAX Method

Description$.ajax()Get data from a remote server using HTTP requests$.get()Use HTTP GET request to get data from remote server$.post()Use HTTP POST request to get data from remote server Get data$.getJSON()Get data in JSON format$.ajaxSetup()Set global AJAX settings$.ajaxError()Handle AJAX Error$.ajaxComplete()Handling the completion event of the AJAX request$.ajaxStart()Handling events when AJAX starts$.ajaxSend() Handling events before AJAX requests are sentHandling events when AJAX requests are successfulHandling events when AJAX endsSet global AJAX settingsThis article introduces the usage of jQuery library in detail, including its basic concepts and syntax and common methods. With this knowledge in hand, developers can write web applications more efficiently. jQuery is currently one of the most popular and concise JavaScript libraries. It provides many powerful APIs for JavaScript, making JavaScript development easier to understand, manage, and extend. By using the jQuery library, developers can easily complete complex tasks, handle various DOM events, perform various effects and AJAX operations, which helps improve the user experience, reliability and response speed of web applications.

##$.ajaxSuccess()
$.ajaxStop()
$.ajaxSetup()
##8. Summary

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