How to put switch statement correctly?

I am trying to use switch instead of if else , can you help me how to put below code in switch statement , i can't figure it out how to !

var computed = {
  idOnly: function() {},
  classOnly: function() {},
  selectAllElements: function() {},
  eitherOne: function() {}
}

Below is where i can not figure out how to put switch statement

if (computed.idOnly(selector)) {
  var getById = document.getElementById(selectorArray[1]);
  Allelements.push(getById);
} else if (computed.classOnly(selector)) {
  var getByClass = document.getElementsByClassName(selectorArray[1]);

  computed.selectAllElements(getByClass, Allelements);
} else {
  var getByTags = document.getElementsByTagName(selectorArray[0]);

  switch (selectorArray.length) {
    case 1:
      computed.eitherOne(getByTags, Allelements);
      break;
    case 2:
      computed.eitherOne(byId, byClass, byTag, false);
      break;
    case 3:
      computed.eitherOne(byId, byClass, byTag, true);
      break;
  }
}

Any help will be much more appreciated , Thanks in advance :)