// JavaScript Document
// email script
function emailCheck (emailStr) {
	/* 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 represents the range of characters allowed as
	   the first character in a valid username or domain.  I just made it
	   the same as above, but if you want to add a different constraint,
	   you would change it here. */
	var firstChars=validChars
	/* 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=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/
	/* The following string represents at atom (basically a series of
	   non-special characters.) */
	var atom="(" + firstChars + validChars + "*" + ")"
	/* The following string represents one word in the typical username.
	   For example, in john.doe@somewhere.com, john and doe are words.
	   Basically, a word is either an atom or quoted string. */
	var word="(" + atom + "|" + quotedUser + ")"
	// The following pattern describes the structure of the user
	var userPat=new RegExp("^" + word + "(\\." + word + ")*$")
	/* 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 course 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("Store Email address seems incorrect (check @ and .'s). Should be like foo@bar.com or foo@bar.com.au")
		return false
	}
	var user=matchArray[1]
	var domain=matchArray[2]

	// See if "user" is valid 
	if (user.match(userPat)==null) {
		// user is not valid
		alert("The username part of the email address doesn't seem to be valid. Please use the format foo@bar.com or foo@bar.com.au")
		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! Please re-enter your email address.")
			return false
			}
		}
		return true
	}

	// Domain is symbolic name
	var domainArray=domain.match(domainPat)
	if (domainArray==null) {
		alert("The domain name of the email address doesn't seem to be valid. Please re-enter your email address. Email address should be like foo@bar.com or foo@bar.com.au")
		return false
	}
	/* domain name seems valid, but now make sure that it ends in a
	   three-letter word (like com, edu, gov) or a two-letter word,
	   representing country (uk, nl).
	   If there's a country code at the end of the address, the full domain
	   must include a hostname and category (e.g. host.co.uk or host.pub.nl).
	   If it ends in a .com or something, make sure there's a hostname.*/

	/* Now we need to break up the domain to get a count of how many atoms
	   it consists of. */
	var atomPat=new RegExp(atom,"g")
	var domArr=domain.match(atomPat)
	var len=domArr.length
	if (domArr[domArr.length-1].length<2 || 
		domArr[domArr.length-1].length>3) {
	   // the address must end in a two letter or three letter word.
	   alert("The email address must end in a three-letter domain, or two letter country. Like foo@bar.com or foo@bar.com.au")
	   return false
	}

	/* If it ends in a country code, we want to make sure there are at
	   least 2 atoms preceding it (representing host and category (i.e.
	   com, gov, etc.)) */
	if (domArr[domArr.length-1].length==2 && len<3) {
	   var errStr="This address ends in two characters, which is a country"
	   errStr+=" code.  Country codes must be preceded by "
	   errStr+="a hostname and category (like com, co, pub, pu, etc.)"
	   alert(errStr)
	   return false
	}

	/* If it just ends in .com, .gov, etc., make sure there's a host name.
	   This case can never actually happen because earlier checks take
	   care of this implicitly, but we'll do it anyway. */
	if (domArr[domArr.length-1].length==3 && len<2) {
	   var errStr="This email address is missing a hostname! Should be like foo@bar.com or foo@bar.com.au"
	   alert(errStr)
	   return false
	}
	// If we've gotten this far, everything's valid!
	return true;
}
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