Minor adjustments

Your code looks great! Nice indenting and highly readable. Though there are some things I would leave out (although I'm more than aware that you have the same intentions after you finish writing the script):
- I would leave out every console.log. It does affect performance in some way;
- I would highly recommend that you avoid mixing languages. In your HTML you have some ID's with a Dutch name in it, but your Javascript is in full english. I would pick one of the two and stick with it. My advice would, obviously, go to full english.