var year, month, day, monthSum = 0;

var arr = new Array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

function getDate() {

    year = Number(prompt("请输入年"));

    month = Number(prompt("请输入你的出生月份"));

    day = Number(prompt("请输入你的出生日期"));

    for (var i = 0; i < month - 1; i++) {

        monthSum = monthSum + arr[i]

    }

    if ((year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)) && month > 2) {

        monthSum = monthSum + day + 1

        document.write("您的生日在" + year + "年" + "是第" + monthSum + "天");

    } else {

        monthSum = monthSum + day

        document.write("您的生日在" + year + "年" + "是第" + monthSum + "天");

    }

}

getDate();