1 <!DOCTYPE html>
2 <html>
3 <head>
4 <meta charset="UTF-8">
5 <title></title>
6 <script type="text/javascript">
7
8 var n1=10;
9 var n2=20;
10
11 var n = n1++; //后置，先赋值，即n=10，再n1自增1为11
12
13 console.log(n); //10
14 console.log(n1); //11
15
16 n = ++n1 //前置，n1先自增1为12，再赋值给n，即n为12
17 console.log(n); //12
18 console.log(n1); //12
19
20 n = n2--; //后置，先把n2赋值给n，即n为20，再自减1，则n2为19
21 console.log(n); //20
22 console.log(n2); //19
23
24 n = --n2; //前置，n2先自减1，即n2为18，再赋值给n，即n为18
25 console.log(n); //18
26 console.log(n2); //18
27
28
29
30 </script>
31 </head>
32 <body>
33 </body>
34 </html>