Booking validation in a big if-elseif block
Conditionals

isValidEmail != false &amp;&amp; isIntPositive != false

I'd make that isValidEmail == true &amp;&amp; isIntPositive == true. You could even short these to isValidEmail &amp;&amp; isIntPositive. This makes your code more readable AND uses less characters (less that has to be read). It's a win-win.

var isIntPositive = procs.isPositiveInteger(guest.value);
... isIntPositive != false &amp;&amp; guest.value &gt; 0 ...


I don't know what isPositiveInteger does, but I have the feeling this check (guest.value &gt; 0) is redundant. If you don't allow 0 then explicitly decline that value with guest.value != 0.

Duplication

You have a lot of message = { ... }. I'd create a separate function that takes the arguments. Then I'd create separate functions for the constants to be wrapped in, so you get things like this:

function createInvalidEmailMessage(){
    return createMessageObject(1, "Error", "Invalid Email Address. Please re-enter valid Address!");
}
function createMessageObject(ref, title, text){
    return {
        "ref": ref,
        "title": title,
        "text": text
    };
}