Regex: Email validation.

HTML

<label for="email" id="email">Hey!</label>
<input id="email" name="email" type="email" class="required" /> 
<span class="msg error">You shall not pass!</span>
<span class="msg success">You can pass!</span>

CSS

.msg {
    display: none;
}
.error {
    color: red;
}
.success {
    color: green;
}

JavaScript

var component = {
    input   : $('input[name="email"]'),
    mensage : {
        fields  : $('.msg'),
        success : $('.success'),
        error   : $('.error')
    }
},
    regex  = /^([a-zA-Z0-9_\-\.]+)@([a-zA-Z0-9_\-\.]+)\.([a-zA-Z]{2,5})$/;

component.input.blur(function () {
    component.mensage.fields.hide();
    regex.test(component.input.val()) ? component.mensage.success.show() : component.mensage.error.show();
});