监听 textarea 的 input 事件的 scrollHeight 变化(scrollHeight 元素内容高度),赋值给 height。
再给 textarea 设置最大最小高度,padding 为 0(它自身的),保证上下限。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
body {
margin: 0;
}
.wrapper {
height: 100vh;
display: flex;
flex-direction: column;
color: white;
}
nav {
height: 60px;
background-color: blue;
position: fixed;
width: 100%;
}
main {
margin-top: 60px;
background-color: pink;
height: 100%;
flex: 1;
}
footer {
background-color: red;
width: 100%;
display: flex;
}
textarea {
min-height: 50px;
max-height: 300px;
padding: 0;
width: 100%;
}
</style>
</head>
<body>
<div class="wrapper">
<nav>nav</nav>
<main>main</main>
<footer>
<textarea></textarea>
</footer>
</div>
<script>
var textarea = document.querySelector("textarea");
textarea.addEventListener("input", (e) => {
textarea.style.height = 50 + "px"; // 删除文本内容,调整高度
textarea.style.height = e.target.scrollHeight + "px";
});
</script>
</body>
</html>