btn.onclick = function(){
//第一步获取输入框里面的值
var date = txt.value;
//第二部获取年份前4位数
var y = parseInt(date/10000);
//第三步获取月份
var m = parseInt(date/100)%100;
//第四部获取天数
var day = date%100;
//定义一个变量用来存储2月份的天数
var sea;
//判断平年闰年
if(y%400==0||(y%4==0&&y%100!=0)){
sea = 29;
}else{
sea = 28;
}
//月份进行比较
switch(m){
case 12:
day+=30;
case 11:
day+=31;
case 10:
day+=30;
case 9:
day+=31;
case 8:
day+=31;
case 7:
day+=30;
case 6:
day+=31;
case 5:
day+=30;
case 4:
day+=31;
case 3:
day+=sea;
case 2:
day+=31;
case 1:
alert(day);
bleak;
default:
alert("输入错误");
}
}