javascript - HTML button to NOT submit form

I have a form. Outside that form, I have a button. A simple button, like this:

Nevertheless, when I click it, it submits the form. Here's the code:

All this button should do is some JavaScript. But even when it looks just like in the code above, it submits the form. When I change the tag button to span, it works perfectly. But unfortunately, it needs to be a button. Is there any way to block that button from submitting the form? Like e. g.

Answer

I think this is the most annoying little peculiarity of HTML... That button needs to be of type "button" in order to not submit.

Update 5-Feb-2019: As per the HTML Living Standard (and also HTML 5 specification):

The missing value default and invalid value default are the Submit
Button state.