javascript 文本验证不起作用。警报消息不显示

Question

我有一个简单的表单验证脚本:

<script language=”javascript”>
    function return validate_form(register)
 {      
if (""==document.forms.register.FNAME.value){
    alert("This field is required!");
    document.forms.register.FNAME.focus();
    return false;
}    
if (""==document.forms.register.LNAME.value){
    alert("This field is required!");
    document.forms.register.LNAME.focus();
    return false;
}
if (EMAIL.value.search( /^[a-zA-Z]+([_\.-]?[a-zA-Z0-9]+)*@[a-zA-Z0-9]+([\.-]?[a-zA-Z0-9]+)*(\.[a-zA-Z]{2,4})+$/ ) == -1){
    alert(“Wrong email”);
    return false;
}       
if('0'==document.forms.register.GENDER.value){
    alert("You must select an option!");
    document.forms.register.GENDER.focus();
    return false;
}
if (""==document.forms.register.ADDRESS.value){
    alert("This field is required!");
    document.forms.register.ADDRESS.focus();
    return false;
}
if (""==document.forms.register.CONTACTNO.value){
    alert("This field is required!");
    document.forms.register.CONTACTNO.focus();
    return false;
}
}
</script>

使用 onSubmit 处理程序调用该函数，但单击“提交”时没有任何反应。它直接进入 PHP 脚本，而不是 javascript '拦截'它。有什么想法吗？

表单 HTML:

 <form name="register" action="register.php" method="POST" onsubmit="return validate_form(register);">
<table width="100%" border="0">
<tr>
  <td width="46%" height="24" align="right">First Name:</td>
  <td width="54%"><input name="FNAME" type="text" size"20" /></td>
</tr>
<tr>
  <td height="24" align="right">Last Name:</td>
  <td><input name="LNAME" type="text" size"20" /></td>
</tr>
<tr>
  <td height="24" align="right">Email Address</td>
  <td><input name="EMAIL" type="text" size"20" /></td>
</tr>
<tr>
  <td height="24" align="right">Gender:</td>
  <td><select name="GENDER">
      <option value="" selected="selected">- Select One -</option>
      <option value="Male">Male</option>
      <option value="Female">Female</option></select></td>
</tr>
<tr>
  <td height="24" align="right">Address:</td>
  <td><input name="ADDRESS" type="text" size"20" /></td>
</tr>
    <tr>
  <td height="24" align="right">Contact No.:</td>
  <td><input name="CONTACTNO" type="text" size"20" /></td>
</tr>
<tr>
  <td height="24" align="right">Password</td>
  <td><input name="PASSWORD" type="password" size"20" /></td>
</tr>
 <tr>
  <td height="24" align="right">Re-type Password</td>
  <td><input name="PASSWORD2" type="password" size"20" /></td>
</tr>
<tr>
<td>&nbsp;</td>
<td><input name="submit" type="submit" value="Register" /></td>
</tr>
</table>

</form>

警报消息不显示？怎么了？？

Answer 1

好吧，我对你的代码进行了一些重构，以使其更有意义和可维护性

html 更改:

<form name="register" action="register.php" method="POST" onsubmit="return validate_form();">

示例 JS:

function validate_form() {
    var frm = document.forms.register;
    function focus_and_false(el) {
        el.focus();
        return false;
    }
    if( frm.FNAME.value === "" ) { /* repeat this for all form elements you want to validate */
        alert("This field is required!");
        return focus_and_false(frm.FNAME); /* this is not the best, but i'm showing you how you can reduce overall code by not rewriting the same things. */
    }
    return true;
}​

and here is a sample