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Understanding The TrimWhitespace() Function In Lucee CFML

Ben Nadel
Published: October 3, 2023

The other day, when I was looking into which whitespace characters are removed by trim(), I came across a Lucee CFML function that I hadn’t seen before: trimWhitespace(). The Function doesn’t have an in-depth description; and, looking at the Java code didn’t immediately clarify the function’s behavior. As such, I wanted to try it out for myself in order to see if the function might be useful to me in the future.

To start building up a mental model, I created a <cfsavecontent> buffer that combined various whitespace and non-space characters in various orders. However, whenever I went to save the file, SublimeText kept trying to trim some of the spaces (which is what I want it to do in most cases). So, instead of using whitespace directly, I used some placeholder characters:

  • + → Space (Chr 32)
  • ~ → Tab (Chr 9)

Then, I replaced these with the proper whitespace character before calling trimWhitespace():

<cfsavecontent variable="buffer">
	cleaned = buffer
		.replace( "+", chr( 32 ), "all" )
		.replace( "~", chr( 9 ), "all" )
		.replace( chr( 9 ), "T", "all" )
		.replace( chr( 10 ), "N", "all" )
		.replace( chr( 32 ), "S", "all" )
	echo( cleaned );

As you can see, I have all manner of whitespace character combinations. And, when we run this Lucee CFML code, we get the following output:


After going back-and-forth between the input and the output, I think I finally understand the rules:

  • Any series of whitespace characters that contains a Newline is collapsed down into a single Newline character.

  • And series of whitespace characters that does not contain a Newline is collapsed down into the first whitespace character in the series.

Ironically, the trimWhitespace() function doesn’t actually “trim” the string (leaving Newlines on both ends in my example). Really, it’s “collapsing” whitespace, not trimming it. That said, I do like the fact that it reduces multiple newlines down into a single newline. I can see that being helpful in various text-processing workflows.

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