Question

我是编程中的新Bie，我正在创建一个代码，通过该代码，我如何限制用户在定义的数字中输入值。

我希望用户输入不超过35个字符或长度的字段值。

这是我的书面守则，但它无效

我使用onkeyup方法

＆＃13;

function handleChange() {
    var x = document.getElementById("fname");
    var y = document.getElementById("lname");
    if ((x.value > 35) || (y.value > 35))
    {
      alert("value should less than 35");
    }
  }

＆＃13;

<form onkeyup="handleChange()">
    Enter your fname: <input type="text" id="fname">
    Enter your lname: <input type="text" id="lname">
</form>

＆＃13;

Answer 1

您可以使用maxlength属性从HTML中执行此操作。因此您不需要handleChange函数。用户将仅限于设定数量的字符。更多信息：https://www.w3schools.com/tags/att_input_maxlength.asp

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或者你想做什么，但添加.length

所以..

<input type="text" id="fname" maxlength="35">
<input type="text" id="lname" maxlength="35">

Answer 2

<form action="/action_page.php">
  Username: <input onkeydown="handleChange()" id="fname" type="text" name="usrname" maxlength="36"><br>
   Username: <input onkeydown="handleChange()" id="lname" type="text" name="usrname" maxlength="36"><br>
  <input type="submit" value="Submit">
</form>


<script>
function handleChange() {
    var x = document.getElementById("fname").value;
    var y = document.getElementById("lname").value;
    console.log(x);
    if ((x.length > 35) || (y.length > 35))
    {
        alert("value should less than 35");
    }
  }
</script>

Answer 3

应该是：

if ((x.value.length > 35) || (y.value.length > 35))

Answer 4

<form onkeyup="handleChange()">
Enter your fname: <input type="text"  maxlength="35" id="fname">
Enter your lname: <input type="text"  maxlength="35" id="lname">
</form>
<script>
function handleChange() {
    var x = document.getElementById("fname");
    var y = document.getElementById("lname");
    if ((x.value.length > 34) || (y.value.length > 34))
    {
        alert("value should less than 35");
    }
  }
</script>

如何在文本字段长度大于定义的数字时显示警报

4 个答案: