if 写法 ｜ 自己写法

    let year=2022;
    let month = 7;
    let day=11;

    function isRun(year) {
        if((year%4==0 && year%100!=0) || year%400==0) {
            return true;
        }
        return false;
    }
    function monthDays(m) {
        if(m == 1 || m==3 || m==5 || m==7 || m ==8 || m==10 || m==12) {
            return 31 + monthDays(m-1);
        }
        if(m ==2) {
            return isRun()? 29 + monthDays(m-1) : 28 + monthDays(m-1);
        }
        if(m==4 || m==6 || m==9 || m==11){
            return 30 + monthDays(m-1);
        }
        return 0;
    }
    
    console.log(day + monthDays(month-1));

switch 写法

    let count=0;

    function isRun(year){
        if (year%400==0||(year%4==0&&year%100!==0)) {
            return true;
        }else{
            return false;
        }
    }
    function Gonedays(year,month,day){
        switch (month) {
            case 12 : count += 30;
            case 11 : count += 31;
            case 10 : count += 30;
            case 9 : count += 31;
            case 8 : count += 31;
            case 7 : count += 30;
            case 6 : count += 31;
            case 5 : count += 30;
            case 4 : count += 31;
            case 3 : count += 28;
                if (isRun(year)){
                    count++;
                };
            case 2 : count += 31;
            case 1 : count += day;
            break;
        }
        console.log(year+"年"+month+"月"+day+"日"+"过了"+count+"天");
    }
    Gonedays(2000,3,11);