// Creates a clone of this object.
Clone()
{
  const joinOns = new LJCJoinOns();
  let joinOn = joinOns.Add("fromColumnName1", "toColumnName1");
  joinOn = joinOns.Add("fromColumnName2", "toColumnName2");

  let clone = joinOns.Clone();
  const result = clone.Count;

  // result:
  // 2
}