<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>contenteditable</title>
<style>
.content{
width:380px;
height:100px;
border:1px solid #e1e1e1;
-webkit-user-modify:read-write-plaintext-only;
}
.content::after {
content: attr(placeholder);
position: absolute;
top: 10px;
color: #a9a9a9;
}
</style>
</head>
<body>
<div class="content" contenteditable="true" placeholder="说点什么吧"></div>
<script src="js/jquery-2.1.4.min.js"></script>
<script>
$('.content').on('input', function(){
var text= $(this).text().trim();
if (text=="") {
$(this).html(""); //会显示placeholder
}
});
</script>编辑框里删除时，会增加<br/>标签，就不会再出现placeholder里的提示内容了，所以使用js做相应处理。