如果我在警报框中单击确定，则所有文本框都为空？

Question

i got error, For example i am having 4 text boxs name,dob,age and mail-id. in this if i entered name,dob and age but i am not entering mail-id. if i click submit the alert box appear in that mail id is empty like that. If i click ok in that alert box rest of the three field name,dob,age also got empty if i click ok.

 <script>
 function validateForm(){
var x=document.forms["registration_form"]["user_name"].value
 if (x==null || x=="")
           {
                alert("Please Enter The Name");
return false;

}
else{ true}
var x=document.forms["registration_form"]["dob"].value
if (x==null || x=="")
           {
                alert("Please Enter Date Of Birth");
                return false;

}
  else{ true}
var x=document.forms["registration_form"]["age"].value
if (x==null || x=="")
           {
                alert("Please Enter Age");
return false;

}
else{ true}
var x=document.forms["registration_form"]["number"].value
if (x==null || x=="")
           {
                alert("Please Enter The Mobile Number");
return false;

}
else{ true}
    var x=document.forms["registration_form"]["mail"].value
var atpos=x.indexOf("@");
var dotpos=x.lastIndexOf(".");
     if (x==null || x=="" || atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length)
             {
                  alert("Please Enter a Valid Mail-Id and Must fill it");
                  return false;

           }
           else{ true}
           var x=document.forms["registration_form"]["address"].value
   if (x==null || x=="")
           {
                  alert("Please Enter The address ");
                return false;

           }
else
{
return true;
}
}      
</script>

Answer 1

remove x==null in your condition check

  else
    {
    true 
    }

this block is unnecessary;

Answer 2

I assume you are calling this function from your form's onSubmit method. If so, ensure you also are using . For example:

<form ... onSubmit="return validateForm()" />
...
</form>

This will ensure that form is not submitted when your validation function returns false.