表单验证 - 在线编辑器

          <form action="tryjs_submitpage.htm" onsubmit="return myFunction()">
  姓名 (最大 10 个字符): <input type="text" id="fname" size="20"><br> 年龄 (从 1 到 100): <input type="text" id="age" size="20"><br> E-mail: <input type="text" id="email" size="20"><br>
  <br>
  <input type="submit" value="提交">
</form>
<script>
  function myFunction() {
    var at = document.getElementById("email").value.indexOf("@");
    var age = document.getElementById("age").value;
    var fname = document.getElementById("fname").value;
    submitOK = "true";
    if (fname.length > 10) {
      alert("姓名不能超过 10 个字符");
      submitOK = "false";
    }
    if (isNaN(age) || age < 1 || age > 100) {
      alert("年龄范围为 1 到 100");
      submitOK = "false";
    }
    if (at == -1) {
      alert("不合法的 e-mail!");
      submitOK = "false";
    }
    if (submitOK == "false") {
      return false;
    }
  }
</script>
        