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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
li {
background-color: blueviolet;
margin-top: 10px;
}
</style>
<title>Document</title>
</head>
<body>
<textarea name="" id="" cols="30" rows="10">123</textarea>
<button>發佈</button>
<ul>
<li>123</li>
</ul>
<script>
var btn = document.querySelector('button');
var text = document.querySelector('textarea');
btn.onclick = function() {
var ul = document.querySelector('ul');
var li = ul.children;
var a = ul.children[li.length - 1].innerHTML;
var b = text.value;
if (text.value == '') {
alert('您沒有輸入內容');
return false;
} else if (a == b) {
alert("拒絕重複發佈");
} else {
var li = document.createElement('li');
li.innerHTML = text.value;
ul.appendChild(li);
ul.insertBefore(li, ul.children[0]);
}
}
</script>
</body>
</html>
