Functional Programming: Apply Functional Programming to Convert Strings to URL Slugs (!='')

What is does
!== ""
in Solution 1 mean?

function urlSlug(title) {
  return title
    .filter(obj => {
      return obj !== "";

The !== operator checks if the value on the left is of the same type and value as the value on the right, and returns either true or false. You might want to check out w3 school’s page on javascript comparisons.