console
function add()
{
var now = new Date();
var div = document.getElementById('box');
div.innerHTML = div.innerHTML + 'time_' + now.getTime() + '<br />';
div.scrollTop = div.scrollHeight;
}
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>滚动条在底部</title>
<link rel="stylesheet" href="css/app.css">
</head>
<body>
<h4>请点击“插入一行”按钮,插入最新信息,当出现滚动条时,滚动条将自动保持在底部。</h4>
<div id="box"></div>
<input type="button" value="插入一行" onclick="add();">
</body>
<script src="js/app.js"></script>
</html>
#box {
overflow: auto;
height: 100px;
width: 400px;
border: 1px solid #999;
}