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<script>
//2.计算某日是这一年的第几天
var y = parseInt(prompt("请输入一个年份"));
var m = parseInt(prompt("请输入一个月份"));
var d = parseInt(prompt("请输入一个日期"));
var f = 0;
switch (m) {
case 12:
f += 31;
case 11:
f += 30;
case 10:
f += 31;
case 9:
f += 30;
case 8:
f += 31;
case 7:
f += 31
case 6: f += 30
case 5: f += 31
case 4: f += 30
case 3: f += 31
case 2: {
y % 4 == 0 && y % 100 != 0 || y % 400 == 0 ? f += 28 : f += 29
}
case 1: f += d
}
alert(f + "天")
</script> -->
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