Core String Functions Will Accept Null / Undefined Values In ColdFusion

In ColdFusion, you can have null / undefined values. You can't directly reference those null values or you'll get a null reference error (NRE); but, you can pass around null values using return-value propagation or the safe-navigation operator. This sometimes leaves me unsure as to how ColdFusion will handle a specific null-value scenario. A while back, I looked at ColdFusion's core decision functions; and it turns out, they all play nicely with undefined values. Today, I wanted to look at the core string functions in ColdFusion to see how they handle null / undefined values.

In a lot of old ColdFusion code, you'll see very cautious traversal of object paths using logic that looks like this:

In this case, we're using the structKeyExists() function to see if the property value exists before subsequently inspecting its length so we don't throw a null reference error. In modern ColdFusion, we can often use the Elvis operator (?:) and / or the safe navigation operator (?.) to simplify our logic. However, since ColdFusion hasn't always played nicely with null / undefined values, it's not always clear what happens when ColdFusion consumes a null value in a function call like len().

It turns out, ColdFusion does exactly what we would hope that it does: treat the value as "empty". That allows us to simplify the above code like this:

It turns out that a lot of the native string-oriented functions in ColdFusion do exactly what we would hope that they do. Here's a quick sanity check - I'm going to consume a null / undefined value in a bunch of ColdFusion functions that assume strings:

If we run these in Lucee CFML 6.2, we get the following output:

If we run these in Adobe ColdFusion 2023, we get the following output:

I tried running this on BoxLang v1.0.0, but get an error:

java.lang.VerifyError: Inconsistent stackmap frames at branch target 2282

As you can see, ColdFusion basically treats null / undefined inputs the same way it would treat the empty string; which is exactly what we would hope that it does when attempting to simplify our logic. In particular, I'm excited to know that I can use len() and val() to safely consume a lot of potentially undefined values in my ColdFusion control flow.

Want to use code from this post? Check out the license.

Short link: https://bennadel.com/4795

Reader Comments

Will Belden May 7, 2025 at 12:00 PM

50 Comments

While I like most of it (variables?.undefined) I can't say I'm a fan of hash() returning a value. I can see potential issues there. I think CF gets it "more better" here. It was funny, I immediately said "noooooo" as I was scrolling to change to "ah, that's better" seeing the CF result.

For me, it's ACF for work and 100% Lucee for non-work or anything "new" like a personal biz. (And by "100%" Lucee I mean "if I'm not using non-CFML" like a JS framework.)

Ben Nadel May 7, 2025 at 12:11 PM

16,020 Comments

@Will,

Yeah, the hash() one struck me as strange too on the Lucee side. I wonder if it's converting to an empty string; or maybe the string literal null. I'll see if I can sus-out which thing it's doing.

re: side-project stuff, I'm the opposite - Lucee at work, ACF in personal life. That's primarily because I use managed hosting. If I actually knew something about server management, I would have more options.

Are you managing your own servers?

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