can you explain the difference between a parent node and a parent element node through this code?
<body>
<ul id="parent">
<li></li>
<li id="mi"></li>
<li></li>
</ul>
<script>
//
var mi = document.getElementById("mi");
//
var parent1 = mi.parentNode;
console.log(parent1);
//
var parent2 = mi.parentElement;
console.log(parent2);
var html = document.documentElement;
console.log(html.parentNode);//
console.log(html.parentElement);//null
</script>
</body>