Functional Programming: Apply Functional Programming to Convert Strings to URL Slugs Bug?

The freeCodeCamp compiler is saying:

urlSlug(" Winter Is Coming") should return “winter-is-coming”.

But when I run it in Atom, I do get “winter-is-coming”.

Here is my code:

// the global variable
var globalTitle = "Winter Is Coming";

// Add your code below this line
function urlSlug(title) {
  return title.split(/\s+/g).map(x => x = x.toLowerCase()).join("-");
// Add your code above this line

var winterComing = urlSlug(globalTitle); // Should be "winter-is-coming"

Test against many samples. For example, if the string was

"   Winter is Coming"

What will your function produce?