Redirect to an other page doesn’t work.

From the documentation on these pages I would assume I can just put the following code in the “footer” of my site…..but it doesn’t work. Why can’t you just add a spot to the messages or mail tab where we can put in a url and have it redirect? I know…..that’s just way too easy…..

https://contactform7.com/dom-events/
https://contactform7.com/redirecting-to-another-url-after-submissions/

  document.addEventListener( 'wpcf7submit', function( event ) { // or maybe wpcf7mailsent?
alert('asdfsadfsadfsadf');
    document.location = 'my_url';
  }, false );