Thank you!

I like your regex solution! I learned a lot from it.

notes/reminders for my benefit:

1. replace returns a copy of the given string with modifications according to two parameters, target-to-change and replacement values.
2. .replace method accepts a call back function that takes the result from matches as arguments. so when the regex finds a match it can perform the task of converting each match toUpperCase.
3. logic of your regex: match any lower case character that appears at the start of a string or directly after a whitespace. - I like it!

I like how simple this is.
As a beginner i'm still writing out the long version and explicitly declaring statements, so this is very useful to see the shorthand versions of the same thing.

note for my benefit:
learnings from yours:

1. brackets not necessary for simple conditional test.
2. '!' operator understood as 'not true' is the same as '=== false'.

Yes, the input number will only be natural numbers. However, for the result, it will be float number. The one in the expected ... to equal ... is the result from running your solution function (left) and the expected answer (right).