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Validate an email address. (advanced)

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The following JavaScript will validate an email address using strict rules when a form is submitted.

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  1. ...
  2.  
  3. <head>
  4.  
  5. ...
  6.  
  7. <script language="JavaScript" type="text/javascript">
  8. function emailCheck(emailStr) {
  9.      var checkTLD=1;
  10.      var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;
  11.      var emailPat=/^(.+)@(.+)$/;
  12.      var specialChars="\\(\\)><@,;:\\\\\\\"\\.\\[\\]";
  13.      var validChars="\[^\\s" + specialChars + "\]";
  14.      var quotedUser="(\"[^\"]*\")";
  15.      var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
  16.      var atom=validChars + '+';
  17.      var word="(" + atom + "|" + quotedUser + ")";
  18.      var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
  19.      var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");
  20.      var matchArray=emailStr.match(emailPat);
  21.      if (matchArray==null) {
  22.           alert("You must supply a valid email address.");
  23.           return false;
  24.      }
  25.      var user=matchArray[1];
  26.      var domain=matchArray[2];
  27.      for (i=0; i<user.length; i++) {
  28.          if (user.charCodeAt(i)>127) {
  29.              alert("The supplied email user name contains invalid characters.");
  30.          return false;
  31.          }
  32.      }
  33.      for (i=0; i<domain.length; i++) {
  34.         if (domain.charCodeAt(i)>127) {
  35.             alert("The supplied email domain contains invalid characters.");
  36.             return false;
  37.         }
  38.      }
  39.      if (user.match(userPat)==null) {
  40.          alert("The supplied email address contains invalid characters.");
  41.          return false;
  42.      }
  43.      var IPArray=domain.match(ipDomainPat);
  44.          if (IPArray!=null) {
  45.              for (var i=1;i<=4;i++) {
  46.                  if (IPArray[i]>255) {
  47.                  alert("The supplied email IP address is invalid.");
  48.                  return false;
  49.              }
  50.          }
  51.          return true;
  52.      }
  53.      var atomPat=new RegExp("^" + atom + "$");
  54.      var domArr=domain.split(".");
  55.      var len=domArr.length;
  56.      for (i=0;i<len;i++) {
  57.          if (domArr[i].search(atomPat)==-1) {
  58.              alert("The domain name does not seem to be valid.");
  59.              return false;
  60.         }
  61.      }
  62.      if (checkTLD && domArr[domArr.length-1].length!=2 &&
  63.          domArr[domArr.length-1].search(knownDomsPat)==-1) {
  64.          alert("The supplied email address must end in a well known domain or two letter " + "country code.");
  65.          return false;
  66.      }
  67.      if (len<2) {
  68.          alert("The supplied email address is missing a hostname.");
  69.          return false;
  70.      }
  71.      return true;
  72. }
  73. </script>
  74.  
  75. ...
  76.  
  77. </head>
  78. <body>
  79.  
  80. ...
  81.  
  82. <form id="form1" name="form1" method="post" onSubmit="return emailCheck(this.email.value)" action="">
  83.  
  84. ...

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