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10.08.2008 at 01:58PM PDT, ID: 23799137
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8.7

Help with email address validation checker - allow two periods but ensure text exists after last period

Asked by Bishork in JavaScript, Scripting Languages

Tags:

I am new to javascript.  I need to edit my email validation function to allow two dots but make sure that the last dot still has something after it.

The code I am working with is given below FIRST,  the second code snippet function is an email validator i found on the web.  It allows for two periods, and makes sure that there is something after the final "."  But since I'm new to js I'm having trouble understanding why it works.  

Can someone please explain to me?  Is -1 the FIRST position in the field or is 0 the first position?  Which part of the second snippet I pasted allows for two dots as well as not allowing it to pass if there is nothing after the final .

My code doesn't return "joe.joe@joe." as invalid
but the one i found on the web does.

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function checkForValidEmailAddress(emailAddressField) 
{
	var emailAddress = emailAddressField.value;
	
	// Do not throw an error if the field is blank.
	if ("" == emailAddress) 
	{
		return true;
	}
	
	var at = "@";
	var dot = ".";
	var positionOfAtSymbol = emailAddress.indexOf(at);
	var lengthOfAddress = emailAddress.length;
 
	// Check to see if an "@" character exists.
	// If it does exist, it should not be as 
	// the first or last character of the address.
	if (emailAddress.indexOf(at) == -1 
		|| emailAddress.indexOf(at) == 0 
		|| emailAddress.indexOf(at) == lengthOfAddress - 1)
	{
		emailAddressField.select();
		emailAddressField.focus();
		return false;
	}
 
	// Check to see if an "." character exists.
	// If it does exist, it should not exist as 
	// the first or last character of the address.
	if (emailAddress.indexOf(dot) == -1 
		|| emailAddress.indexOf(dot) == 0 
		|| emailAddress.indexOf(dot) == lengthOfAddress - 1 )
	{
		emailAddressField.select();
		emailAddressField.focus();
		return false;
	}
 
	// Make sure that there is a second "." character.
	if (emailAddress.indexOf(at,(positionOfAtSymbol + 1)) != -1)
	{
		emailAddressField.select();
		emailAddressField.focus();
		return false;
	}
 
	// Make sure that a "." character does not immediately
	// preceed or follow the "@" character.
	if (emailAddress.substring(positionOfAtSymbol - 1, positionOfAtSymbol) == dot 
		|| emailAddress.substring(positionOfAtSymbol + 1, positionOfAtSymbol + 2) == dot)
	{
		emailAddressField.select();
		emailAddressField.focus();
		return false;
	}
 
	// Make sure there exists at least one "." 
	// character after the "@" character.
	if (emailAddress.indexOf(dot,(positionOfAtSymbol + 2)) == -1)
	{
		emailAddressField.select();
		emailAddressField.focus();
		return false;
	}
 
	// Make sure there is no whitespace within the address.
	if (emailAddress.indexOf(" ") != -1)
	{
		emailAddressField.select();
		emailAddressField.focus();
		return false;
	}
 
	return true;				
}
 
 
<script language = "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
 }
 
Keywords: Help with email address validation chec…
Title
1 javascript submit()
2 Javascript
3 quick website code snippets
4 js countdown
5 Include js files
6 Converting a JavaScript Snippet to a c…
 
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[+][-]10.08.2008 at 02:15PM PDT, ID: 22673542

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About this solution

Zones: JavaScript, Scripting Languages
Tags: javascript
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Solution Provided By: robacarp
Participating Experts: 1
Solution Grade: A
 
 
[+][-]10.13.2008 at 06:16AM PDT, ID: 22702084

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