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# Discussion on: Solving "Spinal Tap Case" / freeCodeCamp Algorithm Challenges

## Replies for: thanks for the thorough explanation on that! 🤯🤯

willsmart

No worries, hope it helps!

BTW I've updated the main line of code from `/(?<=[a-z])(?=[A-Z])...` to `/(?<=[A-Za-z])(?=[A-Z])...` matching the explanation below (sort of changed my mind on that halfway through writing).

Using `[A-Za-z]` just makes sure that SentencesContainingAWordWithOneLetter get translated correctly.
Of course it breaks support for CONSTANT_CASE, but what can you do?

How do you like this?

``````const spinalCase = s =>
s.replace(
/(?<=[Aa-z])(?=[A-Z][a-z])|(?<=[a-z])(?=A)|[^A-Za-z]+/g
, '-'
)
.toLowerCase()

spinalCase('SentencesContainingAWordWithOneLetter CONSTANT_CASE')
// 'sentences-containing-a-word-with-one-letter-constant-case'
``````
willsmart

Well, it's a trade-off. On the one hand "AAAA" is the word "A" four times in UpperCamelCase, on the other hand it's the word "AAAA" in CONSTANT_CASE. In the end the problem is just ambiguous.

You've solved the tradeoff by only breaking camelcase words where the next word has more than one char
That may be a fair strategy since it means that constant case is well covered, but does mean some pretty reasonable camel case sentences won't work. ("ThisIsASpinalTap" -> "this-isa-spinal-tap" )

In the end, it's about figuring out which cases are important and what rules you want to cover.

I think a good medium might be to take blocks of uppercase letters surrounded by non-letters, and stop them from being clobbered as camel case words by lowercasing them.

``````f = s => s
.replace(
/(?<=[^A-Za-z]|^)[A-Z]+(?=[^A-Za-z]|\$)/g,
w=>w.toLowerCase()
)
.replace( // edited to handle numbers a bit
/(?<=[A-Za-z])(?=[A-Z0-9])|(?<=[0-9])(?=[A-Za-z])|[^A-Za-z0-9]+/g,
'-'
).toLowerCase()

a=[
"ThisIsASpinalTapAAAA",
"THIS_IS_A_SPINAL_TAP_A_A_A_A",
"thisIsASpinalTapAAAA",
"this-is-a-spinal-tap-a-a-a-a",
"this is a spinal tap a a a a"
]
a.map(f)
// -> [
"this-is-a-spinal-tap-a-a-a-a",
"this-is-a-spinal-tap-a-a-a-a",
"this-is-a-spinal-tap-a-a-a-a",
"this-is-a-spinal-tap-a-a-a-a",
"this-is-a-spinal-tap-a-a-a-a"
]

``````