How to Validate E-mail Addresses in javascript (javascript email validating)

HTML & CSS Tutorials

How to Validate E-mail Addresses in javascript (javascript email validating)

How to Validate E-mail Addresses in javascript (javascript email validating)

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Contributed by Joe

Friday, 21 July 2006

How to Validate E-mail Addresses in javascript (javascript email validating)

How to conform to a format of a valid email address, you should think about the following logic:

Syntax Check-Validates the address for syntax, whether it has all of the mandatory characters present (e.g. @) and any illegal characters present (i.e. ~). It will also check for multiple occurrences of required characters (i.e. @@).
DNS/MX Record Check-Validates the domain name with DNS server to ensure that the email domain is a valid registered domain.
Mail Server Check-Validates an email address (e.g. ) by mail server (e.g. mail.devx.biz) to ensure that the mail server indeed has the email address. This method has very good performance. (Attention: a few mail servers don't support this method(e.g. yahoo))

But to java script,we only can do Syntax Check-Validates,see ollowing logic:

Check if the e-mail address is empty; if it is, the field is not valid.
Check for illegal characters, and if they occur, the field is not valid.
Check if the @ symbol is missing; if it is, the field is not valid.
Check for the occurrence of a dot; if there is none, the field isn’t valid.
Otherwise, the field is valid.

Example of How to Validate E-mail Addresses in javascript

Create a function for validating an e-mail address.

function checkEmail(email) {
if (email.length == 0) {
window.alert(“You must provide an e-mail address.”);
return false;
}
if (email.indexOf(“/”) > -1) {
window.alert(“E-mail address has invalid character: /”);
return false;
}
if (email.indexOf(“:”) > -1) {
window.alert(“E-mail address has invalid character: :”);
return false;
}
if (email.indexOf(“,”) > -1) {
window.alert(“E-mail address has invalid character: ,”);
return false;
}
if (email.indexOf(“;”) > -1) {
window.alert(“E-mail address has invalid character: ;”);
return false;
}
if (email.indexOf(“@”) < 0) {
window.alert(“E-mail address is missing @”);
return false;
}
if (email.indexOf(“\.”) < 0) {
window.alert(“E-mail address is missing .”);
return false;
}
return true;
}

Create another function named checkForm

\It takes a form object as an argument. The function should call checkEmail and pass it the value of the field containing the e-mail address and then return the result returned by the checkEmail function:

function checkForm(formObj) {
return checkEmail(formObj.myField.value); }

Create an email field

Create a form that contains a field for entering the e-mail address and uses the onSubmit event handler to call the checkForm function:

<body>
<form name=”myForm” action=”target.html”
onSubmit=”return checkForm(this);”>
E-mail: <input type=”text” name=”myField”><br>
<input type=”submit”>
</form>
</body>

How to Validate Credit Card Numbers with javascript

You should consider following logic when validate credit card

Check if the credit card number is empty
Check the length of the credit card number
Check for nonnumeric characters
Otherwise, the field is valid.

See following code

function checkCreditCard(card) {
if (card.length == 0) {
window.alert(“You must provide a credit card number.”);
return false;
}
card = card.replace(“ “,””);
if (card.substring(0,1) == “4”) {
if (card.length != 13 && card.length != 16) {
window.alert(“Not enough digits in Visa number.”);
return false;
}
} else if (card.substring(0,1) == “5” && (card.substring(1,2) >= “1” && card.substring(1,2) <= “5”))
{
if (card.length != 16) {
window.alert(“Not enough digits in MasterCard.”);
return false;
}
} else if (card.substring(0,1) == “3” && (card.substring(1,2) == “4” || card.substring(1,2) == “7”))
{
if (card.length != 15) {
window.alert(“Not enough digits in American Expr.”);
return false;
}
} else {
window.alert(“This is not a valid card number.”);
return false;
}
for (i=0; i<card.length; i++) {
if (card.charAt(i) < “0” || card.charAt(i) > “9”) {
window.alert(“CCard must only contain numbers.”);
return false;
}
}
return true;
}

Last Updated ( Friday, 28 July 2006 )

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