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Editorial Team
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Asked: 2026-05-27T05:30:21+00:00

I am using ColdFusion 9.0.1 I recently read that in ColdFusion 9, it is

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I am using ColdFusion 9.0.1

I recently read that in ColdFusion 9, it is now advised to use isNull() and not use isDefined().

I didn’t find much info on this at all around the web.

Is there any advantage to using one or the other in ColdFusion 9?

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  1. Editorial Team

    I know that in general people have been moving away from it for some time. The main use for it was to determine whether a variable existed in a particular scope, but structKeyExists() is more precise for that. IsDefined() works very hard to find any possible instance of the variable you’ve asked for. (Sean Corfield had a bit to say about structKeyExists vs. isDefined.)

    I’ve not seen anywhere a recommendation to use isNull() instead of isDefined. Actually, I would have expected isNull to return an error if you give it an undefined variable, but apparently that works.

    How do you do dynamic variables, though?

    structKeyExists(form,"address_" & i)

    You can try array notation…

    isNull(form["address_" & i])

    …but if i is undefined this throws an error.

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