This list helps you to determine where your visitors are from. Now that you understand how e-mail addresses should be formatted, you can write code to validate these formats and to catch common mistakes.
Based on the standard format for e-mail addresses, a few assumptions can be made about any e-mail address that is entered in your form:
• Must be non-zero length
• Must have one and only one @ character
• Must contain at least one period character
• May not contain any spaces
The first part of the validation code checks the last three conditions by using common string manipulation functions. You have already checked the length of the e-mail address, so you do not need to repeat that task.
Checking for a Single @ Character
The quickest way to verify that only one @ character was used in an e-mail address is to write a loop that reads the entire string and looks for the @ character. The code that performs this task follows:
Dim i
Dim iAtCount
iAtCount = 0
sTemp = frmDataEntry.parm_sender_email.Value
For i = 1 To Len(sTemp)
If Mid(sTemp, i, 1) = "@" Then
iAtCount = iAtCount + 1
If iAtCount > 1 Then
Alert "Your e-mail address can only contain one @ character."
frmDataEntry.parm_sender_email.focus
Exit Sub
End If
End If
Next ' Next i
if iAtCount <> 1 Then
Alert "Your e-mail address must contain an @ character."
frmDataEntry.parm_sender_email.focus
Exit Sub
End If
The For loop starts at the beginning of the e-mail address and watches for @ characters. If it gets more than one, it stops immediately and generates an error message. If the loop gets to the end of the e-mail address and no @ character was found, a different error message is shown to the user.
Checking for a Period Character
This task is essentially the same as checking for the @ character, except for the fact that finding more than one period is not necessarily an error. To add the code for this validation, change the loop that you created to check for @ characters. The code from the previous validation with a few minor changes is as follows:
Dim i
Dim iAtCount
Dim iPeriods
iAtCount = 0
iPeriods = 0
sTemp = frmDataEntry.parm_sender_email.Value
For i = 1 To Len(sTemp)
If Mid(sTemp, i, 1) = "@" Then
iAtCount = iAtCount + 1
If iAtCount > 1 Then
Alert "Your e-mail address can only contain one @ character."
frmDataEntry.parm_sender_email.focus
Exit Sub
End If
ElseIf Mid(sTemp, i, 1) = "." Then
iPeriods = iPeriods + 1
End If
Next ' Next i
if iAtCount <> 1 Then
Alert "Your e-mail address must contain an @ character."
frmDataEntry.parm_sender_email.focus
Exit Sub
End If
If iPeriods < 1 Then
Alert "Your e-mail address must contain at least one period."
FrmDataEntry.parm_sender_email.focus
Exit Sub
End If
Adding the two lines of code within the For loop that was already there saves time by checking for both error conditions in the same loop. The code to check for periods is nearly identical to the code that checks for the @ character. If the character is a period, the iPeriods counter increases by one. If, when the loop is done, the iPeriods counter is less than one, an error message is shown to the user.
Checking for Spaces
This final basic check of a user’s e-mail address ensures that no spaces are embedded within the address. Because this code is even simpler than the previous two validations, there is no need for a lengthy explanation. Using the previous block of code, make the following changes:
Dim i
Dim iAtCount
Dim iPeriods
iAtCount = 0
iPeriods = 0
sTemp = frmDataEntry.parm_sender_email.Value
For i = 1 To Len(sTemp)
If Mid(sTemp, i, 1) = "@" Then
iAtCount = iAtCount + 1
If iAtCount > 1 Then
Alert "Your e-mail address can only contain one @ character."
frmDataEntry.parm_sender_email.focus
Exit Sub
End If
ElseIf Mid(sTemp, i, 1) = "." Then
iPeriods = iPeriods + 1
ElseIf Mid(sTemp, I, 1) = " " Then
Alert "Your e-mail address may not contain any spaces."
frmDataEntry.parm_sender_email.focus
Exit Sub
End If
Next ' Next i
if iAtCount <> 1 Then
Alert "Your e-mail address must contain an @ character."
frmDataEntry.parm_sender_email.focus
Exit Sub
End If
If iPeriods < 1 Then
Alert "Your e-mail address must contain at least one period."
FrmDataEntry.parm_sender_email.focus
Exit Sub
End If
After you add the three previous code blocks to your script, you are protected against the most common errors encountered in entering e-mail addresses: spaces, extra @s, and zero period characters.
posted by gonsa VP at 11:08 AM