Email form validation javascript

[Brian2011]

This code will validate an email address to ensure the user enters an email address in the correct format:

<script Language="Javascript">
<!--
function checkform(theform){

var EmailOk = true
var Temp = theform.email
var AtSym = Temp.value.indexOf('@')
var Period = Temp.value.lastIndexOf('.')
var Space = Temp.value.indexOf(' ')
var Length = Temp.value.length - 1
if ((AtSym < 1) ||
(Period <= AtSym+1) ||
(Period == Length ) ||
(Space != -1)){
EmailOk = false
alert('Please enter a valid e-mail address!')
theform.email.focus();
return (false);}

}
//-->
</script>

Example form code:

<form method=" POST" action="/success.htm" onsubmit="return checkform(this)" name="myform">


When this form is submitted, the javascript runs and will only go to '/success.htm' if user enters a correctly formatted email address.

If the user does not enter a correctly formatted email address, a pop up alert box appears to let them know.

 

[nasaboy007]

Keep in mind that client-side validation is just for the sake of user experience and in no way should be depended on. Everything should be revalidated on the server side as well.

 

[Mark Talks]

A nice little script and I can think of several uses where it would be handy in full or in part, such as free forum/site software that don't allow for open source editing and/or PHP support.

But, with users being able to disable JS and/or manipulate it easier, it's definitely got it's risk. Nice little script though

 

[4pm]

sorry to say but this script checks very few things.. for example it will let thru the following bogus emails as valid ones:

a@b@c._
[email protected]
.xyz
*&^%$#@@@@(.)>>


and so on..

you'll also screw the users that input empty space before or after (happen often when copy-pasting) valid email and will be presented with error message..

i would google "javascript email validation" for good ready to use reliable regex example (there are many to choose from) - correct email validation in javacript (as well as in php) could not be implemented effectively without regex imo

 

[Brian2011]

Yeah, the script does have some drawbacks as you mention but it is a good starting point and weeds out most email address input errors. Of course it doesn't work for those who are determined to enter a wrong email address.

I agree that regex would be able to check input to a finer degree but understanding how regex works can be a little daunting for some.

Here's another little bit of code for ASP programmers that will convert text to proper case as there is no built-in function in VBScript to do this:

<%
''''''' FUNCTION TO CAPITALIZE THE FIRST CHARACTER OF EACH WORD IN THE INPUT STRING '''''''''
Function PCase(strInput)
iPosition = 1
Do While InStr(iPosition, strInput, " ", 1) <> 0
iSpace = InStr(iPosition, strInput, " ", 1)
strOutput = strOutput & UCase(Mid(strInput, iPosition, 1))
strOutput = strOutput & LCase(Mid(strInput, iPosition + 1, iSpace - iPosition))
iPosition = iSpace + 1
Loop
strOutput = strOutput & UCase(Mid(strInput, iPosition, 1))
StrOutput = strOutput & LCase(Mid(strInput, iPosition + 1))
PCase = strOutput
End Function
'''''''''''''''''''''''''''''''' END FUNCTION '''''''''''''''''''''''''''''''''''''''''''''''
%>

...so 'peter Smith' or 'PeTER smiTH' becomes 'Peter Smith'

<%
' example
Str = "PeTER smiTH"
Str = PCase(Str)
Response.write(Str)
%>


Hope this is useful to someone

 

[4pm]

basic user-side errors in emails can be handled more accurately in this way:

function checkEmail(s) {
 s = s.replace(/^\s+/, '').replace(/\s+$/, ''); // trim spaces from both ends
 if (!s.length) return !1; // exit early if empty
 var r =/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i; // simple regex, works 99% of time
 return r.test(s); // test & return 
}

the function returns false if the string does not look like email address and true otherwise.
yet the strings like [email protected] still get thru so if you need more robust solution check http://www.regular-expressions.info/email.html for fast examples