Javascript Essentials Part 5

Advanced Email Address Validator

<html>
<HEAD>
<script type="text/javascript">
function echeck(str) {
  var at="@"
  var dot="."
  var lat=str.indexOf(at)
  var lstr=str.length
  var ldot=str.indexOf(dot)
  if (str.indexOf(at)==-1){
     alert("Invalid E-mail ID")
     return false
  }
  if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
     alert("Invalid E-mail ID")
     return false
  }
  if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
      alert("Invalid E-mail ID")
      return false
  }
   if (str.indexOf(at,(lat+1))!=-1){
      alert("Invalid E-mail ID")
      return false
   }
   if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
      alert("Invalid E-mail ID")
      return false
   }
   if (str.indexOf(dot,(lat+2))==-1){
      alert("Invalid E-mail ID")
      return false
   }
   if (str.indexOf(" ")!=-1){
      alert("Invalid E-mail ID")
      return false
   }
   return true          
}
function ValidateForm(){
  var emailID=document.frmSample.txtEmail
 
  if ((emailID.value==null)||(emailID.value=="")){
    alert("Please Enter your Email ID")
    emailID.focus()
    return false
  }
  if (echeck(emailID.value)==false){
    emailID.value=""
    emailID.focus()
    return false
  }
  return true
 }
</script>
</HEAD>
<BODY>
<form name="frmSample" method="post" action="#" onSubmit="return ValidateForm()">
  <p>Enter an E-mail Address : 
    <input type="text" name="txtEmail">  
    <input type="submit" name="Submit" value="Submit">
  </p>
</form>
</body>
</html>

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