I was looking for a fairly basic validation routine to weed out intentional garbage from a form email field. All I came across were either too restrictive or didn’t check what could be checked, so I wrote my own (inspired by various scripts on the web).
// pattern to match email addresses loosely
regex1 = /^[^sn@]*[^sn.@]@[^sn.@][^sn@]*(?=.[^s.n @]+$).[^s.n @]+$/;
// pattern to check for double-dots
regex2 = /(?:..)/;
// get the form value and trim whitespace using jQuery
email_address = jQuery.trim($j("#bus_email").val());
if (!email_address.match(regex1) || email_address.match(regex2))
alert("Please check the email address for accuracy!");
The above regex pattern will look for the following points in an email address:
- Only one @-sign.
- No spaces in the string.
- No newlines/linefeeds in the string.
- One or more characters before the @-sign. The character immediately before @ may not be a period.
- The character immediately after @ may not be a period.
- One or more characters after the @-sign, followed by at least one period followed by one or more characters at the end of the string (for the TLD).
- No two adjacent dots.
The RFC 2822 that defines the email address format is pretty complex, and new TLDs are added from time to time. This script helps to catch typos and randomly entered garbage, but of course has no way to prevent users from entering correctly formed but invalid addresses.
I’m using two separate regular expressions as there doesn’t seem to be a way to negate a string (i.e. two consecutive dots) but only single characters. If someone reading this happens to know how to combine the two regular expressions into one, please let me know!