<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
.inner{
width:100px;
white-space: pre-wrap; /* 自动换行操作 */
}
</style>
</head>
<body>
<textarea id="text"></textarea>
<button id="btn">按钮</button>
<!-- pre 中嵌套 inner -->
<pre id="box"><div class="inner"></div></pre>
<script>
var box = document.getElementById('box');
var btn = document.getElementById('btn');
var text = document.getElementById('text');
btn.onclick = function(){
box.getElementsByTagName('div')[0].innerHTML = text.value ;
}
</script>
</body>
</html>
