Using "continue" To Short-Circuit .each() Iteration In ColdFusion

@Chris,

It's common in a for-in loop, like:

for ( value in values ) {
	if ( value == "boop" ) {
		continue;
	}
	// .... rest of loop
}

But, in my case, with a .each() iterator, the continue is really just acting like a return in the iterator Callback. I wonder if it has to do with how the .each() is being coded under the hood?

@Dirk,

I actually prefer for-in when I can use it. In this case, I was switching from for-in over to .each() so that I could use ColdFusion's ability to perform iteration in parallel threads. Doing so lead to a large increase in throughput; so, while for-in might be faster in general, using .each() proved to be much faster due to the parallelization.

I do like the idea of (key as value in collection) - that would be a cool syntax. I sometimes - at least in Lucee CFML - use the CFLoop tag specifically so I can define multiple variables like:

loop
	key = "local.key"
	value = "local.value"
	struct = payload
	{

	// ... use `key` and `value` here.
}

But, clearly that is more syntacticly verbose.

@All,

I thought maybe the .each() worked with continue because of some loop that was being implemented behind the scenes. As such, I wanted to run a quick test to see if continue would work with a callback even when no loop was in play:

<cfscript>

	visitValues(
		[ "a", "b", "c" ],
		( value ) => {

			if ( value == "b" ) {

				continue; // Seeing if this works.

			}

			writeOutput( value );

		}
	);

	// ------------------------------------------------ //
	// ------------------------------------------------ //

	public void function visitValues(
		required array collection,
		required function callback
		) {

		// NOTE: I'm not using any looping at all here!
		// This is just hard-coded to look for 3-values.
		callback( collection[ 1 ] );
		callback( collection[ 2 ] );
		callback( collection[ 3 ] );

	}

</cfscript>

In this case, there is no loop - my visitValues() method is hard-coded to look at 3 values, passing each item to the given callback. And, when I run this in Lucee CFML and Adobe ColdFusion 2021, they both output:

ac

Both CFML runtimes skipped over the outputting of b due to the continue statement. So, it seems that a loop isn't required to make this quirky behavior possible.

On a somewhat related note, I just accidentally discovered that you can use return to short-circuit a CFML template:

www.bennadel.com/blog/4425-using-return-to-short-circuit-a-cfml-template-in-coldfusion.htm

Normally, I would use exit to halt execution of a CFML template. I wonder if these are doing the same thing under the hood.