Validating email address regular expression with fixed domain

Why use a regular expression when you can test if the string ends with "@gbase.tt"?

But if you really must use a regex, try ^[email protected]$.

I'd start with a full regex for email, like the one found here.

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\]) 

That expression clearly has the @ split in it, so keep the first half, and replace everything after the @ sign with gbase\.tt$.

Keep in mind that you've got to escape the dot since a dot by itself represents any character.

 var x=document.forms["myForm"]["emailId"].value; var atpos=x.indexOf("@abc.com"); var atpos1=x.indexOf("@xyz.in"); var atpos2=x.indexOf("@www.in"); if (atpos<1 && atpos1<1 && atpos2<1) { alert("Not a valid e-mail address"); return false; } 

Here is the solution for fixed domain name and email id containing "." or "_"

you can use pattern - pattern="^[A-Za-z0-9]+(.|_)+[A-Za-z0-9]+@+gmail.com$"

it will only accept email id with domain name gmail.com only