Question

Below I have a Json function and some php code which it retrieves.

JavaScript code:

function postback(){
    if(validation()){
        $.getJSON(
            {"room_no":$("#room").val()},
            function(json){
                $("#roomAlert").html(json.msg)
        });
    }
}

PHP code:

if (isset($_POST['prequestion'])) {
    $roomquery = "
                 SELECT Room
                 FROM Room
                 WHERE
                 (Room = '".mysql_real_escape_string($roomChosen)."')
                 ";

    $roomnum = mysql_num_rows($roomresult = mysql_query($roomquery));
    mysql_close();

    if($roomnum ==0){
        $msg = "This Room is Invalid";
    } else {

        $msg = "";
    }

    $d = array("msg" => $msg);
echo json_encode($d);

}



?>

What my question is that I have a myClickHandler() function and I want it to showConfirm() if the validation() is met and if the postback() function is met if in php $msg = “”; The validation is met but how can I meet the postback() requirement?

Below is the myClickHandler() function:

function myClickHandler(){
     if(validation()){
        showConfirm();
     }
}

Answer 1

You need to use a callback to accomplish this:

function postback(callback){
if(validation()){
    $.getJSON(
        {"room_no":$("#room").val()},
        function(json){
            $("#roomAlert").html(json.msg);
            callback(json.msg);
    });
}

}

function myClickHandler(){
     if(validation()){
        postback(function(message) {
            if (message == "")
                showConfirm();
        });
     }
}

If you are unfamiliar with how callbacks work in JavaScript, check out this article:

http://recurial.com/programming/understanding-callback-functions-in-javascript/