Algorithms in Javascript: CTCI 1.3 URLify: Write a function to create an URL by replacing all spaces of an URL string with %20

ctci-1.3-urlify-1.js

const createUrl = (s1) => {
  let s1Array = s1.split(' ');
  let len = s1Array.length - 1;
  if(s1Array[len] === '') {
    s1Array.pop();
    s1 = s1Array.join(' ');
    return createUrl(s1);
  }
  return s1Array.join('%20');
}

let u = 'javascript algorithms      ';
console.log(createUrl(u));