输入包含一定范围内的数字
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
</head>
<body>
<form action="demo_form.php"method="get">
请输入数值: <input type="range" name="range1" min="1" max="20" step="4"/><br />
<input type="submit" />
</form>
</body>
</html>