An HTML element id is a global variable

Little relatively unknown fact, if you have an id attribute on an element, you can reference it in this way:

// html
<button id="yo">…</button>

// js
yo.onclick = ...

Furthermore, child elements with a name attribute can be referenced in this way:

// html
<form id="x"> 
  <input name="em"> 
</form>

// js
x.em.onclick = ...

Maybe not your favorite API, but it’s a thing.