Apply Functional Programming to Convert Strings to URL Slugs - not working

Tell us what’s happening:
This code appears to complete the challenge when I log to the console but it won’t allow me to pass the test where " Winter is coming" has a space in front. Is this a bug?

Fill in the urlSlug function so it converts a string title and returns the hyphenated version for the URL. You can use any of the methods covered in this section, and don’t use replace . Here are the requirements:

The input is a string with spaces and title-cased words

The output is a string with the spaces between words replaced by a hyphen ( - )

The output should be all lower-cased letters

The output should not have any spaces

Your code so far

// Only change code below this line
function urlSlug(title) {

let prepareString = title.toLowerCase();
let arr = prepareString.split(" ");

if (arr[0] == ''){

let result = arr.join("-")

return result;

urlSlug(" Winter Is Coming")

// Only change code above this line

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.66 Safari/537.36.

Challenge: Apply Functional Programming to Convert Strings to URL Slugs

Link to the challenge:

Failing case has multiple spaces between words, but your code only handles first empty space.

You should filter empty values:

let arr = prepareString.split(" ").filter(Boolean);

That makes sense. Thank you!