<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
#textarea {
width: 100px;
min-height: 20px;
max-height: 70px;
outline: 0;
border: 1px solid #397EFF;
font-size: 13px;
overflow-x: hidden;
overflow-y: auto;
-webkit-user-modify: read-write-plaintext-only;
}
[contentEditable=true]:empty:not(:focus):before {
content: attr(data-text);
}
</style>
</head>
<body>
<div id="textarea" contenteditable="true" data-text="输入内容..."></div>
</body>
</html>
原文：https://www.cnblogs.com/mcll/p/11549679.html