10.2 添加节点

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <script>
    function addNode() {
        var div = document.getElementById("testDiv");
        var textNode = document.createTextNode("123");
        var element = document.createElement("p");
        element.appendChild(textNode);
        div.appendChild(element);
    }
    </script>
</head>
<body>
<p>JavaScript</p>
<div id="testDiv">
</div>
<button onclick="addNode()">click</button>
</body>
</html>