//计算某日是该年的第几天?
var iYear = parseInt(prompt(‘请输入一个年:’));
var iMonth = parseInt(prompt(‘请输入一个月:’));
var iDate = parseInt(prompt(‘请输入一个日:’));
var sum = 0;
switch(iMonth){
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 : sum += iYear % 4 == 0 && iYear % 100 || iYear % 400 === 0 ? 29 : 28;
case 2 : sum += 31;
case 1 : sum += iDate;
}
console.log(iYear + '年' + iMonth + '月' + iDate + '日是' + iYear + '年中的第' + sum + '天');
}