Validate email address textbox using JavaScript

Question

I have a requirement to validate an email address entered when a user comes out from the textbox.
I have googled for this but I got form validation JScript; I don't want form validation. I want textbox validation.
I have written below JScript but "if email invalid it's not returning the same page".

 function validate(email) {

            var reg = /^([A-Za-z0-9_-.])+@([A-Za-z0-9_-.])+.([A-Za-z]{2,4})$/;
            //var address = document.getElementById[email].value;
            if (reg.test(email) == false) 
            {
                alert('Invalid Email Address');
                return (false);
            }
 }

Answer 1

Assuming your regular expression is correct:

inside your script tags

function validateEmail(emailField){
        var reg = /^([A-Za-z0-9_-.])+@([A-Za-z0-9_-.])+.([A-Za-z]{2,4})$/;

        if (reg.test(emailField.value) == false) 
        {
            alert('Invalid Email Address');
            return false;
        }

        return true;

}

in your textfield:

<input type="text" onblur="validateEmail(this);" />