How about
$("span:not(:has(*))")
Selects all spans that have no children.
Explanation
The :has() selector “selects elements which contain at least one element that matches the specified selector.” The wildcard * means all elements.
The expression
$('div:has(p)')matches a<div>if a<p>exists
anywhere among its descendants, not just as a direct child.
The :not() selector “selects all elements that do not match the given selector.”
In this case, :has() selects everything and then we use :not() to find the elements that don’t match “everything”… in other words, nothing.
Demo