var date =Number(prompt('请输入一个组成为年月日的八位数','如20160211'))
var year =parseInt(date/10000);
var month =parseInt(date/100)-year*100;
var days =date-(year*10000 + month*100);
var sum =0;
switch(month){
case 12:
sum+=30;
case 11:
sum+=31;
case 10:
sum+=30;
case 9:
sum+=31;
case 8:
sum+=31;
case 7:
sum+=30;
case 6:
sum+=31;
case 5:
sum+=30;
case 4:
sum+=31;
case 3:
if(year%4==0 && year%100!=0 || year%400==0){
sum+=29
}else{
sum+=28
}
case 2:
sum+=31;
case 1:
sum+=days;
break;
default:
alert('你输入的日期不符合规范')
}
alert(date + '是' + year +'年第'+ sum +'天')
