wouldnt type coercion make the parameters when called a number?

It seems like a little bit overkill

Else.....

I don't think this is best practice, because of the following reasons:

1. In my opinion the requirements state that the input is a number, it is not necessary to check.
2. When the input is not of type number the the function does nothing at all.

MDN polyfill rules :D

You're right. Some warriors (and so do I) did this kata on December, so that is the reason why it worked :)

Read the description thoroughly and you'll see why it's solved as is :-)

this is not your month) I'm sorry) but if you interested it you can read about class date and his another functions

I think this solution only works for one month of the year. It certainly fails for me.

You shouldn't define methods on the constructor since every new instance would have its own seperate methods. This would cause unnecessary memory consumption and degraded performance.

You should define these methods on the prototype property of the Vector function, instead.