The content of this article is to introduce how to use jQuery? What are jQuery selectors? Let everyone understand the use of the jQuery file library, the use of basic syntax, and the jQuery selector. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
1. How to use
The jQuery library is located in a JavaScript file, which contains all jQuery functions.
When a web page needs to use jQuery, you need to introduce jQuery's js file into the web page first.
nbsp;html> <meta> <title>My Test JQuery</title> <script></script>
2. jQuery syntax
jQuery syntax is to select HTML elements and perform certain operations on the selected elements. [Recommended related video tutorials: jQuery Tutorial]
Basic grammar form:
$(selector).action()
Example:
$("p").hide() // 隐藏所有 <p> 元素 $("#myInfo").hide() // 隐藏所有 id="myInfo" 的元素
Writing:
All jQuery functions are located in a document.ready function. As shown below.
This is to prevent jQuery code from running before the document is fully loaded (ready), that is, the DOM cannot be manipulated until the DOM is loaded.
If you run the function before the document is fully loaded, the operation may fail.
$(document).ready(function(){ // 代码部分写在这里 });
can also be abbreviated as follows:
$(function(){ // 这里写代码 });
Example:
nbsp;html> <meta> <title>My Test JQuery</title> <script></script> <script> $(function(){ $("button").click(function(){ $("#myDiv1").html("Hello JQuery World"); $("#myDiv1").css("background-color","green"); }); }); </script> <button>点击</button> <div>Hello</div>
3. Basic selector
(1) Element Selector: The jQuery element selector selects elements based on their names.
Example: Use the element selector to select all
elements and hide them.
nbsp;html> <meta> <title>My Test JQuery</title> <script></script> <script> $(function(){ $("button").click(function(){ $("p").hide(); }); }); </script> <button>点击</button> <p>p元素1</p> <p>p元素2</p> <div>Hello</div>
(2) #id selector: jQuery #id selector selects the specified element through the id attribute of the HTML element.
The id of the element in the page should be unique, so if you want to select the only element in the page, you need to use the #id selector
Example: Use the #id selector to select id="myDiv1 " element to hide it.
nbsp;html> <meta> <title>My Test JQuery</title> <script></script> <script> $(function(){ $("button").click(function(){ $("#myDiv1").hide(); }); }); </script> <button>点击</button> <p>p元素1</p> <p>p元素2</p> <div>Hello</div>
(3) .class selector: The jQuery class selector can find elements through the specified class.
Example: Use the class selector to select the element with Class="myClass1" and hide it.
nbsp;html> <meta> <title>My Test JQuery</title> <script></script> <script> $(function(){ $("button").click(function(){ $(".myClass1").hide(); }); }); </script> <button>点击</button> <p>p元素1</p> <p>p元素2</p> <div>Hello</div> <div>你好</div>
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实现方法:1、用“$("img").delay(毫秒数).fadeOut()”语句,delay()设置延迟秒数;2、用“setTimeout(function(){ $("img").hide(); },毫秒值);”语句,通过定时器来延迟。

修改方法:1、用css()设置新样式,语法“$(元素).css("min-height","新值")”;2、用attr(),通过设置style属性来添加新样式,语法“$(元素).attr("style","min-height:新值")”。

区别:1、axios是一个异步请求框架,用于封装底层的XMLHttpRequest,而jquery是一个JavaScript库,只是顺便封装了dom操作;2、axios是基于承诺对象的,可以用承诺对象中的方法,而jquery不基于承诺对象。

增加元素的方法:1、用append(),语法“$("body").append(新元素)”,可向body内部的末尾处增加元素;2、用prepend(),语法“$("body").prepend(新元素)”,可向body内部的开始处增加元素。

在jquery中,apply()方法用于改变this指向,使用另一个对象替换当前对象,是应用某一对象的一个方法,语法为“apply(thisobj,[argarray])”;参数argarray表示的是以数组的形式进行传递。

删除方法:1、用empty(),语法“$("div").empty();”,可删除所有子节点和内容;2、用children()和remove(),语法“$("div").children().remove();”,只删除子元素,不删除内容。

去掉方法:1、用“$(selector).removeAttr("readonly")”语句删除readonly属性;2、用“$(selector).attr("readonly",false)”将readonly属性的值设置为false。

on()方法有4个参数:1、第一个参数不可省略,规定要从被选元素添加的一个或多个事件或命名空间;2、第二个参数可省略,规定元素的事件处理程序;3、第三个参数可省略,规定传递到函数的额外数据;4、第四个参数可省略,规定当事件发生时运行的函数。


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