get child element by class or tag

by greatCar

HTML

<div id="d1">
<p  class = "sup"  id="sup">
test1
</p>
</div>


<div id="d2">
<p class = "sup" id="sup">
test2
</p>
</div>

JavaScript

//https://stackoverflow.com/questions/2899072/javascript-get-child-by-id
 
 let divx = document.getElementById("d2");

 
//let sup =  divx.getElementById("sup");//not working
 
 let sup = divx.getElementsByClassName('sup');//works
   sup = divx.getElementsByTagName('p');//works
 
//sup.style.display = "none";
 sup[0].style.display = "none";

 alert(sup[0].innerHTML);

//sup.value = "xxz";

 alert(sup[0].innerHTML);