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JavaScript: Validate Email Address Using Regular Expressions
How to validate email addresses by checking their format using client-side code.
There are many allowed characters that many email providers do not allow in their email addresses.
This regular expression should cover most if not all emails addresses (note: it does not allow the "/" character unless inside quotes):
var emailrgx = /^(([^<>()[\]\\\/.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
This regular expression allows the "/" character:
var emailrgx = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
Here is an example HTML document using the first regular expression.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Validate Email</title>
</head>
<body>
<p>Enter email address; if red then it is not valid.</p>
<form id="form">
<input type="text" name="email" placeholder="email..." />
</form>
<script type="text/javascript">
var emailrgx = /^(([^<>()[\]\\\/.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
var form = document.getElementById("form");
form.email.addEventListener("keyup", function(event) {
var target = event.target;
if (target.value.length == 0 || target.value.match(emailrgx)) {
target.style.color = "";
}
else {
target.style.color = "red";
}
});
</script>
</body>
</html>
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