Fixed separator bug

[franciscocgoncalves]

When reading your example I noticed that you were inserting a separator after the penultimate element of the array before the lastWord which, in my opinion, isn't appropriate for use in a sentence.

I changed it in the following way.

Behavior before fix:

assert(listify([1, 2, 3, 4]) === '1, 2, 3, and 4');

Behavior after fix:

assert(listify([1, 2, 3, 4]) === '1, 2, 3 and 4');

I also added a validation test that asserts two items with finalWord.

[ljharb]

I'm sorry, but the Oxford comma is required for my module, and is also quite grammatically correct in an English sentence. (for what it's worth, thank you very much for a pull request that's detailed, and includes both the relevant tests and documentation updates!)

[franciscocgoncalves]

To be honest, I didn't know about this so I did a little research. This is what I found out:

• Oxford Comma is used less often in Britain English and accordingly to the University of Oxford Style Guide it should be use to prevent ambiguity but it isn't mandatory;
• in American English, a majority of style guides mandate use of the Oxford Comma;
• the Stylebook published by The Canadian Press for journalistic writing advise against the Oxford Comma;

Some of this information is on Wikipedia.

I'm aware of the controversy of this matter and that it is required on your module, but shouldn't it be optional? If it was not only it would support all the style guides but also other languages like Portuguese.

[ljharb]

@franciscocgoncalves Fair point - I'd be open to accepting a pull request adding an option to omit the Oxford comma, despite personally feeling strongly that it should always be used :-)