![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
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Teacher's comments：
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演示代码如下：
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>dom实战：留言板</title><style>.user{width: 500px;height: 300px;border: 1px solid lightblue;position: relative;top: 10px;padding: 50px;margin: auto;}.textBox{width: 500px;height: 250px;border: 1px solid #CBA4C3;margin: 0 auto;}h3{text-align: center;position: relative;top: 10px;}p{position: absolute;left: 465px;margin-top: 20px;}</style></head><body><!-- <input type="text" onkeydown="console.log(event.key)" placeholder="请输入内容" autofocus><ul class="list"></ul> --><h3>留言板</h3><div class="user"><textarea class="textBox" onkeydown="addMsg(this)" placeholder="请输入内容" cols="30" rows="10" autofocus></textarea><ul class="list"></ul></div><p>感谢您的反馈！</p><script>function addMsg(ele){// console.log(event);// console.log(event.key);if (event.key==='Enter'){// 1. 获取显示留言的容const ul=document.querySelector('.list');//2. 判断用户留言是否为空if (ele.value.trim().length===0){alert('用户留言不能为空');ele.focus();return false;}//3. 添加一条新留言const li=document.createElement('li');//console.log(ele.value);// li.textContent=ele.value;li.innerHTML=ele.value+'<button onclick="del(this.parentNode)">删除</button>';ul.insertAdjacentElement('afterBegin',li);//4. 将输入框中的前一条留言清空ele.value=null;//5. 焦点重置ele.focus();}}//删除function del(ele){// console.log(ele);// ele.remove();return confirm('是否删除?') ? ele.remove() : false;}</script></body></html>
效果如下图：