由于getDay（）获得的结果是0~6的数字，所以要将其转化为我们想要的形式。
数组方式：
var mydate= new Date();
var day=mydate.getDay();
var weekday=["星期日","星期一","星期二","星期三","星期四","星期五","星期六",];
document.write(weekday[day]);//比较方便，要以后注意在其他地方这样使用数组
... JavaScript'''switch方式：
var week = '';
switch(day){
case 0 :
week = '星期一';
break;
case 1 :
week = '星期二';
break;
case 2 :
week = '星期三';
break;
case 3 :
week = '星期四';
break;
case 4 :
week = '星期五';
break;
case 5 :
week = '星期六';
break;
case 6 :
week = '星期天';
break;
}
document.write(week);
... JavaScript'''