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>