Content of api.global survives between 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, where 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
Such variable can be retrieved from the global cache as a 'Filter' object only 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. Accessing the key of a map stored as a global variable in second pass is done using the syntax:
api.global.variable.map[(key)]
Note about global variables:
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).