switch--------case

default总是放在最后,这时default后不需要break语句.并且,default部分也不是必须的,如果没有这一部分,当switch后面圆括号中表达式的值与所有case后面的常量表达式的值都不相等时,则不执行任何一个分支直接退出switch语句.此时,switch语句相当于一个空语句.例如,将上面例子中switch语句中的default部分去掉,则当输入的字符不是"A","B","C"或"D"时,此switch语句中的任何一条语句也不被执行.

 1 function checkDay(){
 2     var now = new Date();
 3     var day = now.getDay();
 4     var week;
 5     switch(day){
 6     case 1:
 7         week = "星期一";
 8         break;
 9     case 2:
10         week = "星期二";
11         break;
12     case 3:
13         week = "星期三";
14         break;
15     case 4:
16         week = "星期四";
17         break;
18     case 5:
19         week = "星期五";
20         break;
21     case 6:
22         week = "星期六";
23         break;
24     case 7:
25         week = "星期日";
26         break;
27     
28     }
29     alert(week);
30 }

第二种情况

 1 function checkDay(){
 2     var now = new Date();
 3     var day = now.getDay();
 4     var week;
 5     switch(day){
 6     case 1:
 7     case 2:
 8     case 3:
 9         week = "星期三";
10         break;
11     case 4:
12     case 5:
13     case 6:
14         week = "星期六";
15         break;
16     case 7:
17         week = "星期日";
18         break;
19     
20     }
21     alert(week);
22 }

 

posted @ 2013-08-23 15:00  最是那一杯红酒  阅读(265)  评论(0)    收藏  举报