Count children of a DOM element

count.js

function countChildren(el) {
  const children = el && el.children;
  if (!children) {
    return 0;
  }
  let count = 0;
  for (let i = 0; i < children.length; i++) {
    const child = children[i];
    count += 1;
    count += countChildren(child);
  }
  return count;
}