In this example, there are no connections for the carrier Air Canada. Technically speaking, when the Form DOM and Data DOM are merged, there simply are no inner rows for “AC.”

 

The comparison with null would fail, because in FormCalc, “null” means “has no value.”

 

What we need in this example is something like “does CONNECTION exist?”

 

In FormCalc, we can ask for the existence of the inner table CONNECTIONS.

 

The EXISTS function is exactly what we need to suppress the inner table if there are no flight connections for the nested CARRIERS table.

 

This figure shows a valuable navigation tip. Select the root node data in the hierarchy and select Events with scripts. All pieces of scripting will be shown at once.

 

Without that knowledge, navigation through the scripting would be cumbersome.