Email validation using JavaScript

<script language = "javascript" >
    function checkEmail() {
        var email = document.getElementById('txtEmail');
        var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
        if (!filter.test(email.value)) {
            alert('Please provide a valid email address');
            email.focus;
            return false;
        }
    }
< /script>

Take a textbox and button in your aspx page and call the JavaScript function on button click.

<input type='text' id='txtEmail'/>
<input type='submit' name='submit' onclick='Javascript:checkEmail();'/>