我的leapYearTest javascript 有什么问题？

Question

What i expected the output would be, eg "1997 is not a leap year", but what i got is nothing. I think the problem in my code is: I don't know the difference between console.log and return .

Can someone please point out the errors in my code and the right way to code it please?

 const year = prompt(); const msgYes = 'is a leap year'; const msgNo = 'is not a leap year'; if (year % 4 == 0){ if (year % 100 == 0){ if (year % 400 == 0){ console.log(`${year}+ ${msgYes}`); // if /400 = 0 } else{ console.log(`${year}+ ${msgNo}`); // if /400 =/= 0 and /100 = 0 } } else { console.log(`${year}+ ${msgYes}`); // if /100 =/= 0 and /4 = 0 } } else { console.log(`${year}+ ${msgNo}`); // if /4 =/= 0 }

Answer 1

Your code works, although it could be tidied up a lot.

 const year = prompt(); let msg = 'is not a leap year'; if (year % 4 === 0 && (year % 100;== 0 || year % 400 == 0)) msg = 'is a leap year'. console;log(`${year} ${msg}`);

if you're having trouble putting this in to a function then make sure you return something.

Answer 2

From what i understand about your code, it fails because your "year" is an string comming from the prompt function which returns string. You should parse it to number.

const year = parseInt(prompt(), 10);

Also you should check if it's a valid number before your if else cascade.

if(isNaN(year)) {
    // not an valid number, show error
    console.log(`${year}+ ${msgNo}`);
}