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Having troubles with my email validation code. I keep on getting the error that my function is not defined. i have made a javascript file for the java code and then i used the onchange in my html to trigger the function.

    <input type="text" id="email" name="email" onchange="check();" />

    function check() {
email = document.getElementById("email").value;
filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
if (filter.test(email.value)) 
    {
    document.getElementById("email").style.border = "3px solid green";  
    return true;
    }
else
    {
    document.getElementById("email").style.border = "3px solid red";
    return false;
    }
}

Having troubles with my email validation code. I keep on getting the error that my function is not defined. i have made a javascript file for the java code and then i used the onchange in my html to trigger the function.

    <input type="text" id="email" name="email" onchange="check();" />

    function check() {
email = document.getElementById("email").value;
filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
if (filter.test(email.value)) 
    {
    document.getElementById("email").style.border = "3px solid green";  
    return true;
    }
else
    {
    document.getElementById("email").style.border = "3px solid red";
    return false;
    }
}

• javascript

Share Improve this question Follow asked Dec 23, 2011 at 0:10 MunLauMunLau 3111 silver badge44 bronze badges 3

• 1 Since when was + an invalid character in email addresses? And why can't a TLD have more than 4 characters in it? – Quentin Commented Dec 23, 2011 at 0:18
• +1 from me. No need to down vote. OP is asking for why getting javascript error which is not even caused by the regex. – Ray Cheng Commented Dec 23, 2011 at 0:21
• Sorry im still not used to the way that i have to post a question – MunLau Commented Dec 23, 2011 at 0:27

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 4

Put your javascript in <script> tags.

Also rename your variable name email since your textbox is using it already.

<input type="text" id="email" name="email" onchange="check();" />
<script type="text/javascript">
    function check() {
        var email_x = document.getElementById("email").value;
        filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
        if (filter.test(email.value)) {
            document.getElementById("email").style.border = "3px solid green";
            return true;
        } else {
            document.getElementById("email").style.border = "3px solid red";
            return false;
        }
    }
</script>

Email validation is not always as simple as your regular expression. Have you looked at:

Validate email address in JavaScript?

A better option would be to use Verimail.js. It's a simple script that takes care of it for you. With Verimail.js you could just do:

var email = "[email protected]";
var verimail = new Comfirm.AlphaMail.Verimail();

verimail.verify(email, function(status, message, suggestion){
    if(status < 0){
        // Incorrect syntax!
    }else{
        // Syntax looks great!
    }
});

The above example will hit the line 'Incorrect syntax!' because of the invalid TLD 'cmo'. Besides this, it will also give a suggestion that you can return to your user, in this case, the suggestion variable will contain '[email protected]' since 'fabeook.cmo' looks a lot like 'facebook.'.

Hope this helps!

Here is the code for html input field and button field

   <input input type="text" name="txtEmailId" id="txtEmailId" /> 
   <input type="submit" class="button" value="Suscribe" name="Suscribe" 
            onclick="javascript:ShowAlert()" />

Now add the below function to the header of your page

 <script type="text/javascript">
 function ShowAlert() {
  var email = document.getElementById('txtEmailId');
  var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
    if (!filter.test(email.value)) {
        alert('Please provide a valid email address');
        email.focus;
        return false;
    }
    else {
        alert("Thanks for your intrest in us, Now you 
        will be able to receive monthly updates from us.");
        document.getElementById('txtEmailId').value = "";
    }
 }
 </script> 

Here you can find the article on this Email Validation in JavaScript

If you are specific about the domains , you may use this code for email validation so as to prevent anonymous email domains.

(^([a-zA-Z]{1,20}[-_.]{0,1}[a-zA-Z0-9]{1,20})(\@gmail\.|\@yahoo\.|\@hotmail\.)$)

You may add additional domains too.

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