JavaScript - SOLO ponerle background rojo a los H2

var x = document.querySelectorAll("h2, div, span");

var i;

for (i = 0; i < x.length; i++) {

  x[i].style.backgroundColor = "red";

}

var x = document.querySelectorAll("h2, div, span");

var i;

for (i = 0; i < x.length; i++) {

    if (x[i].nodeName=="H2") {

        x[i].style.backgroundColor = "red";

    }

}