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How to use jquery event delegation

不言
不言Original
2018-07-09 17:59:061807browse

This article mainly introduces how to use jquery event delegation, which has certain reference value. Now I share it with everyone. Friends in need can refer to it

1. Summary

Summary: Through the on method (event delegation), bind the event to the ancestor of the element to which the event is bound to achieve the effect.

1. What is event delegation?

Through event bubbling, let the event bound to the child element bubble up to the parent element (or ancestor element) and then process it. 

 91       //使用事件委托，只在table上绑定一次事件 
 92       //可以动态绑定事件 
 93       $('table').on('click','td',function(){ 
 94             //$(this).css('background','orange') 
 95             alert('click_td') 
 96       })

2. What are the advantages of event delegation?

Add events to dynamic elements
Events are only bound once, which is highly efficient (for a large number of elements of the same type that need to be bound, the efficiency is very high, such as a table of 2500td, and events must be bound to each td)

 91       //使用事件委托，只在table上绑定一次事件 
 92       //可以动态绑定事件 
 93       $('table').on('click','td',function(){ 
 94             //$(this).css('background','orange') 
 95             alert('click_td') 
 96       })

3. Who is the listening object of event delegation (who is the object of event delegation)?

To execute an event, for example, to bind events to a large number of TDs, the object of the event delegation is its ancestor, which is the table table

 91       //使用事件委托，只在table上绑定一次事件 
 92       //可以动态绑定事件 
 93       $('table').on('click','td',function(){ 
 94             //$(this).css('background','orange') 
 95             alert('click_td') 
 96       })

4, elements added by code and dynamically added What is the difference between elements?

The code to add events to the code generation element must be after the code is generated, so that it can bind events

 73       //如果不是动态创建的，可以直接绑定事件 
 74       $('e388a4556c0f65e1904146cc1a846bee94b3e26ee717c64999d7867364b1b4a3').appendTo($('body')) 
 75       $('e388a4556c0f65e1904146cc1a846bee94b3e26ee717c64999d7867364b1b4a3').appendTo($('body')) 
 76       $('e388a4556c0f65e1904146cc1a846bee94b3e26ee717c64999d7867364b1b4a3').appendTo($('body')) 
 77       $('p').on('click',function(){ 
 78             $(this).css('background','orange') 
 79        })

5. What are the usage scenarios of event delegation?

There are many tds in a table. To bind events to tds, if you use the method of binding events to each td, it is very inefficient and error-prone. It is particularly convenient to use event delegation. One step in place. 

 91       //使用事件委托，只在table上绑定一次事件 
 92       //可以动态绑定事件 
 93       $('table').on('click','td',function(){ 
 94             //$(this).css('background','orange') 
 95             alert('click_td') 
 96       })

6. How to dynamically add rows and columns to a table?

html code append method

 87       $('#btn1').click(function(){ 
 88           $('a34de1251f0d9fe1e645927f19a896e8b6c5a531a458a2e790c1fd6421739d1cb90dd5946f0946207856a8a37f441edfb6c5a531a458a2e790c1fd6421739d1cb90dd5946f0946207856a8a37f441edfb6c5a531a458a2e790c1fd6421739d1cb90dd5946f0946207856a8a37f441edfb6c5a531a458a2e790c1fd6421739d1cb90dd5946f0946207856a8a37f441edfb6c5a531a458a2e790c1fd6421739d1cb90dd5946f0946207856a8a37f441edffd273fcf5bcad3dfdad3c41bd81ad3e5').appendTo('table') 
 89       })

2. How to use jquery event delegation

1. Related knowledge

Event delegation

Through events Bubble, let the event bound by the child element bubble up to the parent element (or ancestor element) and then process it.

2. Code

<!DOCTYPE html>
<html>
<style>
</style>
<head>
    <meta charset="UTF-8">
    <title>演示文档</title>
    <script type="text/javascript" src="jquery-3.1.1.min.js"></script>
    <style type="text/css">
        input{width: 100px;height: 30px;}
        div{width: 50px;height: 50px;border:1px solid green;display: inline-block;margin-left: 15px}
        td{width: 50px;height: 20px;background: #ccc}
      </style>
</style>
</head>
<body>
<h3>jQuery事件对象</h3>
<input id="btn1" type="button" value="事件绑定"><br>
<div></div>
<table>
    <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
</table>
<script type="text/javascript">
    $(function(){
        /*
    //使用事件委托动态绑定事件
      $(&#39;#btn1&#39;).on(&#39;click&#39;,function(){
         $("<div></div>").appendTo($(&#39;body&#39;))
      })
      // $(&#39;div&#39;).on(&#39;click&#39;,function(){
      //     $(this).css(&#39;background&#39;,&#39;orange&#39;)
      // })
      $(document).on(&#39;click&#39;,&#39;div&#39;,function(){
          $(this).css(&#39;background&#39;,&#39;orange&#39;)
      })
      //移出事件委托
      $(document).off(&#39;click&#39;,&#39;div&#39;)
      
      //如果不是动态创建的，可以直接绑定事件
      $(&#39;<div></div>&#39;).appendTo($(&#39;body&#39;))
      $(&#39;<div></div>&#39;).appendTo($(&#39;body&#39;))
      $(&#39;<div></div>&#39;).appendTo($(&#39;body&#39;))
      $(&#39;div&#39;).on(&#39;click&#39;,function(){
            $(this).css(&#39;background&#39;,&#39;orange&#39;)
       })
      
      //每一个td绑定一个事件
      //不能动态的添加事件,效率低
      $(&#39;td&#39;).on(&#39;click&#39;,function(){
          alert(&#39;click_td&#39;)
      })
      */ 
      $(&#39;#btn1&#39;).click(function(){
          $(&#39;<tr><td></td><td></td><td></td><td></td><td></td></tr>&#39;).appendTo(&#39;table&#39;)
      })

      //使用事件委托，只在table上绑定一次事件
      //可以动态绑定事件
      $(&#39;table&#39;).on(&#39;click&#39;,&#39;td&#39;,function(){
            //$(this).css(&#39;background&#39;,&#39;orange&#39;)
            alert(&#39;click_td&#39;)
      })

    })
</script>
</body>
</html>

Add events to dynamic elements
Events are only bound once, high efficiency

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