<!DOCTYPE html>
<html>
<body>
<form action="/demo/html/action_page.php" method="get">
Pick a number between 2 and 5: <input type="number" id="myInput" name="quantity" min="2" max="5" required>
<input type="submit" value="Submit">
</form>
<p>如果您提交表单的数字小于 2 或大于 5，将出现警告消息。</p>
<p><b>注释：</b>Internet Explorer 9 及更早版本或 Safari 不支持 oninvalid 事件。</p>
<script>
document.getElementById("myInput").addEventListener("invalid", myFunction);
function myFunction() { alert("You must pick a number between 2 and 5. You chose: " + this.value);}
</script>
</body>
</html>