My advice is to look into 'type coercion' and while you're at it, 'type conversion' and figure out the difference. It's quite interesting stuff.

how and why does this work ?

Thank you!

If you surround your code with three backticks (```), it will put it in a codeblock, which is far easier readable.

See: https://docs.codewars.com/references/markdown#displaying-code

Added PHP 8.0 support

This also fixes a bug in the solution (see comment on the fork)

Interesting I haven't seen forEach used this way

tests are weak (JS), edge cases like "89,179", "80, 180.0001", "-90,180", etc. should be tested. I've passed with regex that would not work correctly for such edge cases

all tests passes except "99.234, 12.324" and some rendom tests that disappear
but it passed on regex debugger websites and my local machine!
there must be something wrong with tests

Yeah, that caught me off guard too. The description needs a bit of rework.

Because it's easier to do so? If it's solely a number problem then yes, math would be easier. But this kata is more about formatting rather than number checking.

Now it's 6 Kyu :)

Array of coordinates? You only given 1 coordinate per function call.

Slow down buddy. If this feels to much for you, do some easier regex kata first.