JS starting code has an erroneous extra {.

I'm a UK guy. We use Mr. Not sure what the Wikipedia article was saying with that, but it's not right. Likely the same with the suffixes (though it's so rare to see one, I can't speak to experience with that.) I think it just depends on the situation, the context. A TV channel might drop the dots, a legal document might keep them, etc.

Just giving an example isn't enough. There is some amount of spec below that, but some things are left out--making it an incomplete spec. And making the resulting code kinda brittle, that passes only the tests you've written but it would fail other real-world cases.

given John Dallas junior-> J. Dallas Jr
expected 'J. D. Junior' to equal 'J. Dallas Jr'

It's not mentioned anywhere that prefix/suffix checking should be case-insensitive.

Random tests:

given Mrs. Mohammad Eugenia Carlos McLaughlin Sr -> Mrs M. E. C. McLaughlin Sr
expected 'Mrs M. E. C. Mclaughlin Sr' to equal 'Mrs M. E. C. McLaughlin Sr'

given Santino Marlen Hosea O'Hara Jr -> S. M. H. O'Hara Jr
expected 'S. M. H. O\'hara Jr' to equal 'S. M. H. O\'Hara Jr'

It is unclear how the spec Every element of the returning string should be capitalized should be interpreted with name parts containing multiple uppercase letters.

And in the end, no matter what the expected behaviour is, it should be in the fixed tests to make sure it's tested. Sometimes it does not appear in the random tests.

Prefix + First Name + Last Name + Suffix

the string can include more than one First Name

These two statements in description contradict with each other. It should be "one or more First Name(s)".

Preloaded prefixes and suffixes are arrays like this:

[ 'Mister', 'Mr.', 'Mr', 'Madame', 'Mrs.', 'Mrs', 'Miss', 'Ms.', 'Ms' ]

How are we supposed to comprehend this data structure? When I see Mister I do not know what it's supposed to map to, unless I refer to the expected result or the description. (Or in other words, these preloaded arrays are pretty useless.)