In a Javascript program that runs within WSH and creates objects, let's say Scripting.FileSystemObject or any arbitrary COM object, do I need to set the variable to null when I'm finished with it? Eg, am I recommended to do this:
var fso = new ActiveXObject("Scripting.FileSystemObject");
var fileStream = fso.openTextFile(filename);
fso = null; // recommended? necessary?
... use fileStream here ...
fileStream.Close();
fileStream = null; // recommended? necessary?
Is the effect different than just letting the vars go out of scope?
Assigning null to an object variable will decrement the reference counter so that the memory management system can discard the resource - as soon as it feels like it. The reference counter will be decremented automagically when the variable goes out of scope. So doing it manually is a waste of time in almost all cases.
In theory a function using a big object A in its first and another big object B in its second part could be more memory efficient if A is set to null in the middle. But as this does not force the mms to destroy A, the statement could still be a waste.
You may get circular references if you do some fancy class design. Then breaking the circle by hand may be necessary - but perhaps avoiding such loops in the first place would be better.
There are rumours about ancient database access objects with bugs that could be avoided by zapping variables. I wouldn't base my programming rules on such voodoo.
(There are tons of VBscript code on the internet that is full of "Set X = Nothing"; when asked, the authors tend to talk about 'habit' and other languages (C, C++))