How to remove repeated entries from an array while preserving non-consecutive duplicates?

Question

I have an array like var arr = [5, 5, 5, 2, 2, 2, 2, 2, 9, 4, 5, 5, 5]; I really want the output to be [5,2,9,4,5]. My logic for this was:

Answer 1

A bit hackey, but, hell, I like it.

var arr = [5, 5, 5, 2, 2, 2, 2, 2, 9, 4, 5, 5, 5];
var arr2 = arr.join().replace(/(.),(?=\1)/g, '').split(',');

Gives you

[5,2,9,4,5]

Admittedly this will fall down if you're using sub-strings of more than one character, but as long as that's not the case, this should work fine.