Validate and Get Json of a Form with Jquery

I am developing a way to get a json from all Input that are in a div determined with jQuery em>. This is almost finalized I need only one detail and I want to not show me the json until all fields are validated and also if I do not complete a field that returns me a message I'm missing fill a certain field. I show the code ...

$.fn.DataForms = function(){
var $_model = []
var input = $(this).find('input, textarea, select');
var isComplate = true;
$(input).each(function(ev){
    if($(this).attr('type') === "radio"){
        if($(this).validateCheck()){
            $_model += $(this).attr('name') + ": '" + $(this).val() + "',"
        }else{
            $('.alert').alertBang('Falta seleccionar una opcion ${$(this).attr('name')}');
            isComplate = false;
        }
    }else if($(this).context.localName === "select"){
        if($(this).validateSelect()){
            $_model += $(this).attr('name') + ": '" + $(this).val() + "',"
        }else{
            $('.alert').alertBang('Falta seleccionar la opcion deseada ${$(this).attr('name')}');
            isComplate = false;
        }
    }else{
        if($(this).validate()){
            $_model += $(this).attr('name') + ": '" + $(this).val() + "',"
        }else{
            $('.alert').alertBang('Falta rellenar el campo ${$(this).attr('name')}');
            isComplate = false;
        }
    }
})
$_model = JSON.stringify("[{" + $_model + "}]");
$_model = $_model.replace( /"{/gi, '{');
$_model = $_model.replace( /}"/gi, '}')
$_model = $_model.replace(',}', '}');
$_model = $_model.replace( /,null/gi, '');
$_model = eval($_model)
$_model = eval($_model)
if(isComplate === true){
     return $_model;
 }else{
     return 
 }
}

The Validate () functions are functions created by me that are responsible for seeing if the field was filled in or selected, otherwise it will return false , and the function < em> AlertBang () shows me the message I'm passing you.

My problem concretely is that if we have two 3 input of type radio it is valid for one and for the other 2 it does not. Therefore I would return an alert that a field is not selected and json would never come to light.