filter

filter(predicate: Expr, Expr)

filter evaluates to it's second argument if it's first argument evaluates to true, otherwise it does not pass any events. Note: When the predicate transitions from false to true then filter will immediatly evaluate to the last value of it's second argument that it saw.

e.g.

filter(load("[enabled]"), load("[thing]"))

Passes on updates to "[thing]" only if "[enabled]" is true