Number.isNaN 不适用于输入验证

Question

我有问题。

当用户在 input 中输入非数字的内容时，我想显示一条提示“您有问题”。

function function1() {
  var x = document.getElementById("number1").value;
  if (Number.isNaN(x)) {
    alert("you have a problem");
  }

}

<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>Mohsen Yeganeh</title>
  <link rel="stylesheet" href="style.css" />
</head>

<body>
  <input type="text" id="number1">
  <button type="submit" onclick="function1()">click me</button>


</body>

</html>

但是，它不起作用。哪里出错了？

Answer 1

Number.isNaN() checks whether the argument is NaN,不是是否是数字

Number.isNaN(NaN) // true
Number.isNaN("Hello World!") // false, "Hello World!" != NaN

您应该改用 isNaN()，它会检查参数是否为数字：

function function1() {
  var x = document.getElementById("number1").value;
  if (isNaN(x)) {
    alert("you have a problem");
  }
}

<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>Mohsen Yeganeh</title>
  <link rel="stylesheet" href="style.css" />
</head>

<body>
  <input type="text" id="number1">
  <button type="submit" onclick="function1()">click me</button>


</body>

</html>

Number.isNaN 不适用于输入验证

Number.isNaN not working for input validation

html

javascript

css

numbers

function