list merge for previously sorted JS linked lists. utilizes my Linked List class

list_merge.js

function merge(list1, list2){

  var output = new LinkedList();

  while(list1 != null | list2 != null){
    console.log("asdf");
    if (!list2){
      output.add(list1.value);
      list1 = list1.next;
    } else if (!list1){
      output.add(list2.value);
      list2 = list2.next;
    } else if (list1.value < list2.value){
      output.add(list1.value);
      list1 = list1.next;
    } else if (list2.value < list1.value | !list1.value){
      output.add(list2.value);
      list2 = list2.next;
    } else {
      output.add(list1.value);
      list1 = list1.next;
      list2 = list2.next;
    }
  }
  console.log(output);
  return output;
}


var list1 = {value:1, next:{value:2, next:{value:4, next:{value:8, next:null}}}};
var list2 = {value:1, next:{value:3, next:{value:6, next:{value:8, next:{value:20, next:null}}}}};