<ol id="myList">

    <li>Tea</li>

    <li>Milk</li>

    <li>Water</li>

</ol>

<p>点击按钮创建 LI 元素</p>

<p id="demo"></p>

<button onclick="myFunction()">尝试一下</button>

<script>

function myFunction(){

    var x = document.createElement("LI");

    var t = document.createTextNode("Coffee");

    x.appendChild(t);

    document.getElementById("myList").appendChild(x);

}

</script>

​