changing all css selectors on page with js

Question

im trying to use a dom event trigger using tag manager to run a script that will change all the on page elements with the same css selector

this is the JS loop im trying to run:

<script>
     function dissapper() {
   var e = document.getElementsByClassName('form-disappear');
    for (var i = 0; i < e.length; i++) {
        e[i].style.display="none";
    }
}
  function appear() {
   var e = document.getElementsByClassName('form_appear');
    for (var i = 0; i < e.length; i++) {
        e[i].style.display="block";
    }
}

</script>

any idea why its not working?

Answer 1

so al i needed to fix this was to add a function call at the end like so:

<script>
     function dissapper() {
   var e = document.getElementsByClassName('form-disappear');
    for (var i = 0; i < e.length; i++) {
        e[i].style.display="none";
    }
}
  function appear() {
   var e = document.getElementsByClassName('form_appear');
    for (var i = 0; i < e.length; i++) {
        e[i].style.display="block";
    }
}
dissapper()
appear()
</script>

thank you @nulldev for pointing it out.