Help with JavaScript Function: Print out the next 20 leap years

Question

I have a question for school that is stumping me. I don't have an editor to run the JavaScript in, so I am using CodeAcademy and JSFiddle to run it. Both are saying "Un-expected 'else' found.

QUESTION: Write a function that takes ANY year given by user, and prints out the NEXT 20 leap years.

Can someone please look over my code and see if its correct?

Thanks!

var year = prompt("please input a year to find out the next 20 years");
var counter = 20;
var result=true;


function leapyear(year, counter, result) {
    while (counter >= 0) {

        if ((year % 4 === 0) && (year % 100 !== 0)||(year % 400 === 0)); {
            result = true;
            console.log(year);
            year++;
            counter--;
        } 
        else {
        year++;
        }    
    }
}

Answer 1 · 2015-06-16T22:58:31Z

June 16, 2015 10:58pm

Hi Jeff,

As Jason mentioned, syntax wise your code works. But, there are a bunch of logic errors present such that, at the moment, your function doesn't do what you need it to. No worries, though, because I can help with that.

Take a look at all the comments I put! :)

var year = prompt("please input a year to find out the next 20 leap years");
var counter = 20;
//no need for a result variable

//can have two arguments, first is the year entered by user
//second is how many leap years to display
function leapyear(years, num) {
    //convert years to integer
    years = parseInt(years);
    //cache reference to original number of leap years to be shown
    //for use in return statement
    var origNum = num;
    //add 1 to years just in case current year is leap year
    years++;
    //this string will hold all of the leap years
    var leapYears = '';
    //while num is above 0
    while (num > 0) {
        //if years is a multiple of 4 and years is not evenly divisible by 100
        //or years is evenly divisible by 100 and evenly divisible by 400
        //it is a leap year
        if (years % 4 === 0 && (years % 100 !== 0 || ( years % 100 === 0 && years % 400 === 0))) {
            //if at the last year
            if (num === 1) {
                //add a period to end
                leapYears += years + ".";
            }
            else {
                //otherwise, add a comma and space for other years
                leapYears += years + ", ";
            }
            //increase years
            years++;
            //decrease num
            num--;
        }
        else {
            //if not a multiple of 4, just add to years
            years++;
        }
    }
    //returns sentence after while loop is done
    return "The next " + origNum + " leap years are " + leapYears;
}

//write to document the result of running leapyear
document.write(leapyear(year, counter));
//or
//alert result of running leapyear
//alert(leapyear(year, counter));

Answer 2 · 2015-06-16T22:08:03Z

June 16, 2015 10:08pm

The only problem I see is you have a semi-colon after the "if" declaration and before its opening curly brace. Remove that and it should be okay.

Answer 3 · 2015-06-16T22:35:39Z

June 16, 2015 10:35pm

So I would actually do the following:

var year = prompt("please input a year to find out the next 20 years");
var counter = 20;
var result=true;


    while (counter >= 0) {

        if ((year % 4 == 0) && (year % 100 != 0)||(year % 400 == 0)) {
            result = true;
            console.log(year);
            year++;
            counter--;
        } 
        else {
        year++;
        }    
    }

Here is the reason,

You had your counter wrapped in a function and had no way of calling the function after a value was put in, it wasn't really needed. Also, you are right about your === versus ==. It should be noted that === requires the variables to be the same type. So it will only compare string to a string. So if you have "2004" as a string and you compare it to 2004 as an integer even though == returns true, === would return false because the variables are not the same type. You can use either or, but you have to make sure you are getting rid of variable type issues before you can use === or !== for that matter.

The code I put in does output values. To test it, just get to your console using the developer tools in your browser and you'll be able to run the code inline.

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Help with JavaScript Function: Print out the next 20 leap years

Jeff Ward

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3 Answers

Marcus Parsons

Marcus Parsons

Jeff Ward

Jeff Ward

Marcus Parsons

Marcus Parsons

Jeff Ward

Jeff Ward

Marcus Parsons

Marcus Parsons

Jeff Ward

Jeff Ward

Marcus Parsons

Marcus Parsons

Jeff Ward

Jeff Ward

Jeff Ward

Jeff Ward

Marcus Parsons

Marcus Parsons

Jeff Ward

Jeff Ward

Marcus Parsons

Marcus Parsons

Marcus Parsons

Marcus Parsons

Jason Anders

Jason Anders

Jeff Ward

Jeff Ward

Gareth Borcherds

Gareth Borcherds

Jeff Ward

Jeff Ward

Jeff Ward

Jeff Ward

Gareth Borcherds

Gareth Borcherds

Jeff Ward

Jeff Ward