https://opentutorials.org/course/1375/6665

<ul>
    <li>HTML</li>
    <li>CSS</li>
    <li id="active">JavaScript</li>
</ul>
<script>
    var li = document.getElementById('active');
    console.log(li.constructor.name);
    var lis = document.getElementsByTagName('li');
    console.log(lis.constructor.name);
</script>

// HTMLLIElement 단수
// HTMLCollection 복수 (유사배열)