querySelectorAll
by MaddyFiddle
HTML
<div class="correct-class">Div with a correct CSS-class</div>
<div class="wrong-class">Div with a wrong CSS-class</div>
<div id="correctID">Div with a correct ID</div>
<div id="wrongID">Div with a wrong ID</div>
<div class="classone result myid aos"></div>
JavaScript
var correctElements = document.querySelectorAll('#correctID, .correct-class');
document.querySelectorAll('.result')[0].innerHTML = correctElements.length;
const qq = document.querySelectorAll('.aos')
document.getElementById('wrongID').innerHTML = 'selected: ' + qq.length