This is part 11 of the tutorial series Learn Javascript in Construct . This part continues on from part 10. So in case you missed it, see Learn Javascript in Co...
Just in case this is still relevant (for anyone with the same question): check out the fairly new example titled "Generator Function" for one way; but using generator functions is not required, you can just do that too:
for (const inst of runtime.objects.SomeObjectType.instances())
{
if (inst.instVars.SomeInstanceVariable === 42) {...}
}