// Create typed collection from deserialized JavasScript array.
ToCollection()
{
  const array = [
    { FromColumnName: "fromColumnName1", ToColumnName: "toColumnName1" },
    { FromColumnName: "fromColumnName2", ToColumnName: "toColumnName2" },
  ];

  const joinOns = LJCJoinOns.ToCollection(array);
  const result = joinOns.Count;

  // result:
  // 2
}