Argthtjtr

In the mentioned sample code I'm trying to get a value for val variable. I declared it with global scope. And add some console log to verify values. But inside of the function it assign value without problem. But out of the function val is undeclared. why is that?

$.validator.addMethod("serialverify", function(){

                var val;

                $("#serialno").keyup(function(){

                    serial().done(function(data){

                        console.log('final = ' + data);

                        val = data;

                        console.log(val);

                    });

                }); console.log(val);

                return val;

            }, "Please enter valid serial code");

There is a fundamental problem in your code. The assignment is taking place in a callback function, which means it'll only execute when the action keyup is made.

However, the statement return val is happening synchronously.

Suggestion -

You can wrap it in a promise of some sort and resolve it when done is executed. Something on the lines of -

......done( function(data) { ..... resolve(val); })

or declare var val; as global that is outside, the addMethod function