When you are equal parts daring and masochist, give the joke/meme category a try.

Classical JS, since it's innerText, it's been downgraded to a string. So the + will act as concatenation. since -= doesn't make sense for a string, the value is cast into a number. It's the same thing that makes '1' + 1 - 1 == 10 but '1' - 1 + 1 == 1.

JS is fun

@CptFox my post wasn't about that. My post is about how bad the content in the joke/meme category is. I don't really have a problem with that behavior of JS.