js简易留言板

	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
	.wrap {
	width: 400px;
	margin: 30px auto;
	}
	textarea {
	display: block;
	width: 100%;
	height: 60px;
	}
	input {
	display: block;
	width: 60%;
	margin: 15px auto;
	}
	li {
	padding: 5px 10px;
	position: relative;
	word-break: break-all;
	}
	.red {
	color: #000;
	background: #f1f1f1;
	}
	.pink {
	color: #000;
	background: #ccc;
	}
	a {
	position: absolute;
	right: 0;
	top: -20px;
	background: yellow;
	color: #fff;
	}
	#list {
	margin: 0;
	padding: 0;
	list-style: none;
	font: 14px/26px "宋体";
	}
	.clos {
	position: absolute;
	top: 0;
	right: -50px;
	width: 50px;
	color: #fff;
	background: #000;
	padding: 5px 0;
	text-decoration: none;
	text-align: center;
	}
	.clos:hover {

	}
	</style>
	<script type="text/javascript">
	window.onload = function(){
	var btn = document.querySelector('input');
	var text = document.querySelector('textarea');
	var list = document.querySelector('#list');
	var colors = ["red","pink"];
	var nub = 0;
	btn.onclick = function(){
	if(text.value.trim() == ""){
	alert("输入内容不能为空");
	return false;
	}
	var li = document.createElement("li");
	li.innerHTML = text.value;
	// li.className = colors[nub%colors.length];
	/* 判断a标签已经被添加，就让a标签显示出来，否则就添加 */
	if(list.children[0]&&list.children[0].className=="red"){
	li.className = "pink";
	} else {
	li.className = "red";
	}
	var a = null;
	li.onmouseover = function(){
	if(a) {
	a.style.display = "block";
	} else {
	a = document.createElement("a");
	a.href = "javascript:;";
	a.className = "clos";
	a.innerHTML = "删除";
	a.onclick = function (){
	list.removeChild(this.parentNode);
	};
	this.appendChild(a);
	}
	};
	li.onmouseout = function(){
	a.style.display = "none";
	};
	list.insertBefore(li,list.children[0]);
	text.value = "";
	nub++;
	};
	};
	</script>
	</head>
	<body>
	<div>
	<div class="wrap">
	<textarea id="text"></textarea>
	<input type="button" value="留言">
	<ul id="list"></ul>
	</div>
	</body>
	</html>

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