function emailCheck (emailStr) { emailStr = emailStr.toLowerCase() /* 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=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/; /* The following string represents an atom (basically a series of non-special characters.) */ var atom=validChars + '+'; /* The following string represents one word in the typical username. For example, in john.doe@somewhere.com, john and doe are words. Basically, a word is either an atom or quoted string. */ var word="(" + atom + "|" + quotedUser + ")"; // The following pattern describes the structure of the user var userPat=new RegExp("^" + word + "(\\." + word + ")*$"); /* The following pattern describes the structure of a normal symbolic domain, as opposed to ipDomainPat, shown above. */ var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$"); /* Finally, let's start trying to figure out if the supplied address is valid. */ /* Begin with the coarse pattern to simply break up user@domain into different pieces that are easy to analyze. */ var matchArray=emailStr.match(emailPat); if (matchArray==null) { /* Too many/few @'s or something; basically, this address doesn't even fit the general mould of a valid e-mail address. */ alert("Email address seems incorrect (check @ and .'s)"); return false; } var user=matchArray[1]; var domain=matchArray[2]; // Start by checking that only basic ASCII characters are in the strings (0-127). for (i=0; i127) { alert("Ths username contains invalid characters."); return false; } } for (i=0; i127) { alert("Ths domain name contains invalid characters."); return false; } } // See if "user" is valid if (user.match(userPat)==null) { // user is not valid alert("The username doesn't seem to be valid."); return false; } /* if the e-mail address is at an IP address (as opposed to a symbolic host name) make sure the IP address is valid. */ var IPArray=domain.match(ipDomainPat); if (IPArray!=null) { // this is an IP address for (var i=1;i<=4;i++) { if (IPArray[i]>255) { alert("Destination IP address is invalid!"); return false; } } return true; } // Domain is symbolic name. Check if it's valid. var atomPat=new RegExp("^" + atom + "$"); var domArr=domain.split("."); var len=domArr.length; for (i=0;i