Super simple email validation with javascript

The least possible greedy validation you an do is with this RegExp /^\S+@\S+\.\S+$/

It will only ensure that the address fits within the most basic requirements you mentioned: a character before the @ and something before and after the dot in the domain part (\S means "anything but a space"). Validating more than that will probably be wrong (you always have the chance of blacklisting a valid email).

Use it like this:

function maybeValidEmail (email) { return /^\S+@\S+\.\S+$/.test(email); }

What others have suggested should work fine, but if you want to keep things simple, try this:

var booking_email = $('input[name=booking_email]').val();

if( /(.+)@(.+){2,}\.(.+){2,}/.test(booking_email) ){
  // valid email
} else {
  // invalid email
}

Even if you decide to go with something more robust, it should help you understand how simple regex can be at times. :)