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Array: join()

With join you join all elements of an array into a string: 
let words = ['Sex', 'Drugs', 'Rock', 'Roll'];
let s1 = words.join();
let s2 = words.join(' & ');
let s3 = words.join(' and ');
Without an argument join joins the elements separated by commas. s1 has the value 'Sex,Drugs,Rock,Roll'. Otherwise, the passed argument specifies the separator. s2 has the value 'Sex & Drugs & Rock & Roll' and s3 has the value 'Sex and Drugs and Rock and Roll'.

Exercise

Write a function list that takes an array of words and returns a string by concatenating the words in the array, separated by commas and - the last word - by an 'and'. An empty array should return an empty string.

Example: list(['Huey', 'Dewey', 'Louie']) should return 'Huey, Dewey and Louie'.
Create a new array without the last element. Join the elements of this new array with a comma. Append the last element of the original array. Handle edge cases separately.
function list(words) {

  if (words.length === 0) {
    return '';
  }

  if (words.length === 1) {
    return words[0];
  }

  let wordsExLast = words.slice(0, words.length - 1);
  let lastWord = words[words.length - 1];
  return wordsExLast.join(', ') + ' and ' + lastWord;
}

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