<HEAD>
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
function emailCheck (emailStr) {
/* The following variable tells the rest of the function whether or not
to verify that the address ends in a two-letter country or well-known
TLD. 1 means check it, 0 means don't. */
var checkTLD=1;
/* The following is the list of known TLDs that an e-mail address must end with. */
var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;
/* The following pattern is used to check if the entered e-mail address
fits the user@domain format. It also is used to separate the username
from the domain. */
var emailPat=/^(.+)@(.+)$/;
/* The following string represents the pattern for matching all special
characters. We don't want to allow special characters in the address.
These characters include ( ) < > @ , ; : \ " . [ ] */
var specialChars="\\(\\)><@,;:\\\\\\\"\\.\\[\\]";
/* The following string represents the range of characters allowed in a
username or domainname. It really states which chars aren't allowed.*/
var validChars="\[^\\s" + specialChars + "\]";
/* The following pattern applies if the "user" is a quoted string (in
which case, there are no rules about which characters are allowed
and which aren't; anything goes). E.g. "jiminy cricket"@disney.com
is a legal e-mail address. */
var quotedUser="(\"[^\"]*\")";
/* The following pattern applies for domains that are IP addresses,
rather than symbolic names. E.g. joe@[123.124.233.4] is a legal
e-mail address. NOTE: The square brackets are required. */
var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
/* The following string represents an atom (basically a series of non-special characters.) */
var atom=validChars + '+';
/* The following string represents one word in the typical username.
For example, in [email][email protected][/email], john and doe are words.
Basically, a word is either an atom or quoted string. */
var word="(" + atom + "|" + quotedUser + ")";
// The following pattern describes the structure of the user
var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
/* The following pattern describes the structure of a normal symbolic
domain, as opposed to ipDomainPat, shown above. */
var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");
/* Finally, let's start trying to figure out if the supplied address is valid. */
/* Begin with the coarse pattern to simply break up user@domain into
different pieces that are easy to analyze. */
var matchArray=emailStr.match(emailPat);
if (matchArray==null) {
/* Too many/few @'s or something; basically, this address doesn't
even fit the general mould of a valid e-mail address. */
alert("Email address seems incorrect (check @ and .'s)");
return false;
}
var user=matchArray[1];
var domain=matchArray[2];
// Start by checking that only basic ASCII characters are in the strings (0-127).
for (i=0; i<user.length; i++) {
if (user.charCodeAt(i)>127) {
alert("Ths username contains invalid characters.");
return false;
}
}
for (i=0; i<domain.length; i++) {
if (domain.charCodeAt(i)>127) {
alert("Ths domain name contains invalid characters.");
return false;
}
}
// See if "user" is valid
if (user.match(userPat)==null) {
// user is not valid
alert("The username doesn't seem to be valid.");
return false;
}
/* if the e-mail address is at an IP address (as opposed to a symbolic
host name) make sure the IP address is valid. */
var IPArray=domain.match(ipDomainPat);
if (IPArray!=null) {
// this is an IP address
for (var i=1;i<=4;i++) {
if (IPArray[i]>255) {
alert("Destination IP address is invalid!");
return false;
}
}
return true;
}
// Domain is symbolic name. Check if it's valid.
var atomPat=new RegExp("^" + atom + "$");
var domArr=domain.split(".");
var len=domArr.length;
for (i=0;i<len;i++) {
if (domArr[i].search(atomPat)==-1) {
alert("The domain name does not seem to be valid.");
return false;
}
}
/* domain name seems valid, but now make sure that it ends in a
known top-level domain (like com, edu, gov) or a two-letter word,
representing country (uk, nl), and that there's a hostname preceding
the domain or country. */
if (checkTLD && domArr[domArr.length-1].length!=2 &&
domArr[domArr.length-1].search(knownDomsPat)==-1) {
alert("The address must end in a well-known domain or two letter " + "country.");
return false;
}
// Make sure there's a host name preceding the domain.
if (len<2) {
alert("This address is missing a hostname!");
return false;
}
// If we've gotten this far, everything's valid!
return true;
}
// End -->
</script>
</HEAD>
<BODY>
<form name=emailform onSubmit="return emailCheck(this.email.value)">
Your Email Address: <input type=text name="email"><br>
<input type=submit value="Submit">
</form>
