jquery怎么获取文本框的Maxlength

在js里做入力项目长度检查，请问用jquery怎么获取文本框的Maxlength 。

img

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
</head>

<body>
    <input type="text" maxlength="200" id="demo">
    <id id="txt"></id>
</body>
<script>
    let txt = document.getElementById("demo");

    //js写法
    js_text = txt.getAttribute("maxlength")

    // jquery 写法
    jquery_text = $("#demo").attr('maxlength');

    $("#txt").html("<br />js_text:" + js_text + "<br />");
    $("#txt").append("jquery_text:" + jquery_text + "<br/>");
</script>

</html>

设置了的话 获取 dom.maxLength 试试

<!DOCTYPE html>
<html lang="en">

<head>
   <meta charset="UTF-8">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Document</title>
</head>

<body>
   <input type="text" maxlength="200" id="txt">
</body>
<script>
   let txt = document.getElementById("txt");
   console.log(txt.maxLength)

   // jquery 写法
  // $("#text").maxLength
</script>

</html>

Maxlength是属性，使用jquery获取属性值：var shuxingzhi = $("#id").attr("Maxlength");可以用去获取任何属性值。