// Clears the collection list.
Clear()
{
  const joinOns = new LJCJoinOns();
  let joinOn = joinOns.Add("fromColumnName1", "toColumnName1");
  joinOn = joinOns.Add("fromColumnName2", "toColumnName2");

  joinOns.Clear();
  const result = joinOns.Count;

  // result:
  // 0
}