JS onclick mobile alternative - onclick deprecated on iOS and Android too

I have this in HTML

<div class="aplplyevent">
  <input type="hidden" name="type" value="" />
  <div class="hidden-div" id="hidden-div">
    Here is my form that is displayd on click and the button APPLY EVENT will disappear!(As long as my form already has a button!)
  </div>
  <span style="display:block"><button class="btn btn-applyevent" onclick="getElementById('hidden-div').style.display = 'block'; this.style.display = 'none'">APPLY EVENT</button></span>

This in CSS:

.hidden-div {
  display: none;
} 

On desktop devices works fine but on iOS and Adroid my main button "APPLY EVENT" do not disappear and I have 2 buttons, the main button(who stop to dissapear) and the form button.

iOS since v8 and now Android too seems to stop support for "onclick".

Can someone please help me? I'm beginner in JS!

JSFiddle Here

from JS onclick mobile alternative - onclick deprecated on iOS and Android too