DOM not working

Question

When i press button == change text in <a> element, whole html disappears. Where is the problem?

Edit: even when i don't chenge the text, just clicking the button, causes the problem
https://code.sololearn.com/WM1uZ1AK2uQ9/?ref=app

Answer 1

add type="button" to your <button> tag: default type is "submit" wich imply form sending on click...

Answer 2

visph yep, already got it, thx