JavaScript: validating an e-mail address without regular expressions

by Rich Costello

HTML

<form action="#" method="post" id="node-webform-2825">
    <div>
        <input type="text" name="email" id="email" />
        <input type="submit" name="submit" value="Test" />
    </div>
</form>

JavaScript

var checkEmail = function(value) {

    var valid = true;

    if (value.indexOf('@') == -1) {
        valid = false;
    } else {

        var parts = value.split('@');
        var domain = parts[1];

        if (domain.indexOf('.') == -1) {

            valid = false;

        } else {

            var domainParts = domain.split('.');
            var ext = domainParts[1];

            if (ext.length > 4 || ext.length < 2) {

                valid = false;
            }
        }

    }


    return valid;

};

var form = document.getElementById('node-webform-2825');

var validate = function(event) {
    event.preventDefault();
    var val = document.getElementById('email').value;
    var valid = checkEmail(val);

    if (!valid) {

        alert('Not a valid e-mail address');
    } else {

        alert('Valid e-mail address');

    }
};

form.addEventListener('submit', validate, false);