List Join

list-join.js

function joinListOfStrings(list = [], separator = ',', conjunction = 'and', oxfordComma = false) {
  switch (list.length) {
    case 0:
      return '';

    case 1:
      return list[0];

    case 2:
      return list.join( (oxfordComma ? ', ' : ' ') + conjunction + ' ');

    default:
      var lastTwoParts = list.splice(-2);
      var easyBit = list.join(separator + ' ') + separator + ' ';
      return easyBit + lastTwoParts.join( (oxfordComma ? ', ' : ' ') + conjunction + ' ');
  }
};

joinListOfStrings();
joinListOfStrings(['Alpha']);
joinListOfStrings(['Alpha', 'Beta']);
joinListOfStrings(['Alpha', 'Beta'], ',', 'or');
joinListOfStrings(['Alpha', 'Beta'], ',', 'or', true);
joinListOfStrings(['Alpha', 'Beta', 'Zeta']);
joinListOfStrings(['Alpha', 'Beta', 'Zeta'], ',', 'or');
joinListOfStrings(['Alpha', 'Beta', 'Zeta'], ',', 'or', true);
joinListOfStrings(['Alpha', 'Beta', 'Zeta'], ' +', 'or', true);

""
"Alpha"
"Alpha and Beta"
"Alpha or Beta"
"Alpha, or Beta"
"Alpha, Beta and Zeta"
"Alpha, Beta or Zeta"
"Alpha, Beta, or Zeta"
"Alpha + Beta, or Zeta"