DOM对象的继承
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
</head>
<body>
<div id="test"></div>
<script>
var test = document.getElementById('test');
console.log(test); // 输出结果：<div id="test"></div>
console.log(test.__proto__); // 输出结果：HTMLDivElement { …… }
</script>
</body>
</html>
