Advantages of the on method in jquery: 1. The on() method can bind events dynamically added to page elements, and the event handlers added are applicable to current and future elements; 2. on() method Adding one or more event handlers to an element at once can improve efficiency.
The operating environment of this tutorial: windows7 system, jquery3.6.1 version, Dell G3 computer.
on() method adds one or more event handlers on the selected element and sub-elements.
Since jQuery version 1.7, the on() method is the new replacement for the bind(), live(), and delegate() methods. This method brings a lot of convenience to the API and is recommended because it simplifies the jQuery code base.
It is troublesome to write separate registration events for a single element
$("p").click(function(){ $(this).hide(); }); $("p").mouseenter(function(){ $(this).css("background","blue"); });
So you can register multiple events at once through on
$("p").on({ click:function(){ $(this).hide(); }, mouseenter:function(){ $(this).css("background","blue"); } }); //还可以合并 $("div").on( "mouseenter mouseleave", function(){ $(this).toggleclass( "current"); })
The methods for binding events with jQuery are Several, it is recommended to use the .on() method for binding, for two reasons:
1. The on() method can bind events dynamically added to page elements
For example, for DOM elements that are dynamically added to the page, events bound with the .on() method do not need to care about when the element that registered the event is added, nor do they need to be bound repeatedly. Some students may be accustomed to using .bind(), .live() or .delegate(). If you look at the source code, you will find that they actually call the .on() method, and the .live() method is in jQuery1. Version 9 has been removed.
Event handlers added using the on() method apply to current and future elements (such as new elements created by scripts).
bind:
function( types, data, fn ) { return this.on( types, null, data, fn ); },
live:
function( types, data, fn ) { jQuery( this.context ).on( types, this.selector, data, fn ); return this; },
delegate:
function( selector, types, data, fn ) { return this.on( types, selector, data, fn ); }
2, on() method once Performance Adding one or more event handlers to elements can improve efficiency
Many articles have mentioned using event bubbling and proxies to improve the efficiency of event binding, but most of them have not listed specific details. There is a difference, so in order to verify, I did a small test.
Assume that 5,000 li's are added to the page, and use chrome developer tool Profiles to test the page loading time.
Normal binding (let’s call it that)
$("li").click(function(){ console.log(this) });
$(document).on("click","li",function(){ console.log(this) })
Binding The execution time of the process
Ordinary binding is equivalent to registering click events separately on li. The memory usage is about 4.2M and the binding time is about 72ms.
.on() binding uses event proxy, only one click event is registered on the document, the memory usage is about 2.2M, and the binding time is about 1ms.
[Recommended learning: jQuery video tutorial, web front-end video】
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实现方法:1、用“$("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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