Global variables are very useful to persist information either:
- between elements within the execution of a logic
- between executions of a logic for a set of items (i.e. PG, PL ...) if
api.retainGlobal = trueis called
This 'retainGlobal' also works for making use of global variables during executions of both 1st and 2nd pass (i.e. dirty pass). BUT given that the second pass is a whole new JST, the global variables are persisted between the 2 passes. The persistence is done in JSON.
So if you have a complex object (such as a 'Filter') and you store it in a global variable, this global variable can be retrieved from the global cache as a 'Filter' object as long as you are in the first pass. But during the second pass, if you retrieve it you will get the JSON representation of this object! Making use of this in your logic might cause errors.