JS this关键字

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="UTF-8">
 5         <title></title>
 6         <style type="text/css">
 7             #box{
 8                 width: 200px;
 9                 height: 500px;
10                 background: gray;
11             }
12             .child{
13                 width: 100%;
14                 height: 100px;
15                 background: red;
16                 border: 1px solid black;
17             }
18         </style>
19     </head>
20     <body>
21         <div id="box">
22             <div class="child"></div>
23             <div class="child"></div>
24             <div class="child"></div>
25         </div>
26     </body>
27         
28         <script type="text/javascript">
29             var box = document.getElementById("box");
30             box.onclick = function(){
31                 this.style.background= "green";
32             }
33         
34 
35 
36         
37         function fun1{
38 
39         }console.log(this);// this 代指 window
40         
41 
42 
43 
44     //   补充知识点：
45     var value = document.getElementsByTagName("div");
46     var  fatherBox = document.getElementById("box");
47     // 获取 box 下面所有的 div 块
48     var childs = fatherBox.getElementsByTagName("div");
49         
50         </script>
51         
52 </html>