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

Using array.filter() you can check if each element is the same as the one before it.

Something like this:

var a = [5, 5, 5, 2, 2, 2, 2, 2, 9, 4, 5, 5, 5];

var b = a.filter(function(item, pos, arr){
  // Always keep the 0th element as there is nothing before it
  // Then check if each element is different than the one before it
  return pos === 0 || item !== arr[pos-1];
});

document.getElementById('result').innerHTML = b.join(', ');