1 <!DOCTYPE html>
2 <html>
3 <head>
4 <meta charset="UTF-8">
5 <title></title>
6 <script type="text/javascript">
7
8 var a = 123;
9 function fun(){
10 alert(a);//undefined
11 var a = 456;
12 alert(a);//456
13 }
14 fun();
15 alert(a);//123
16
17 //---------------------------------------------------
18
19 var b = 123;
20 function fun(){
21 alert("b = "+b);//123
22 b = 456;
23 }
24 fun();
25 alert("b = "+b);//456,全局的b变成了456
26
27 //---------------------------------------------------
28
29 var c = 123;
30 function fun(c){
31 alert("c = "+c);//undefined
32 c = 456;//对外面的c没影响
33 }
34 fun();
35 alert("c = "+c);//123
36
37 //---------------------------------------------------
38
39 var d = 123;
40 function fun(d){
41 alert("d1 = "+d);//789
42 d = 456;
43 }
44 fun(789);
45 alert("d = "+d);//123
46
47
48 </script>
49 </head>
50 <body>
51 </body>
52 </html>
