How to remove duplicate n (line break) from a string and keep only one?

I have a string like this:

This is a sentence.n This is sentence 2.nnnnnn This is sentence 3.nn And here is the final sentence.

What I want to is:

This is a sentence.n This is sentence 2.n This is sentence 3.n And here is the final sentence.

I want to remove all duplicated n characters from a string but keep only one left, is it possible to do like that in javascript ?