I Cant Save Script UI Setting using Script Labels

Hello Experts, please help me to identify the problem, it doesnt save user entries when selecting from dropdown index!, i dont know what wrong i do?! , its my first time trying to save user setting from UI, here is the simple code :

//Save User UI Setting
var savedUISettings = eval(app.extractLabel("usersettings"));

//Simple Dialog
var doc = app.documents[0];
var w = new Window ("dialog");
w.preferredSize.width = 320;
w.text = "Select Currency";


var myBinding = [
    "Ignore", 
    "Right to Left", 
    "Left to Right"
                        ];   
                             
var myCurrecy = [
            "$",
            "£",
            "€",
            "¥"
                        ]; 
                             
var myTitle = w.add ("statictext", undefined, "Select Your Binding and Currenc :");
var myDropdown1 = w.add ("dropdownlist", undefined, myBinding);
var myDropdown2 = w.add ("dropdownlist", undefined, myCurrecy);

myDropdown1.selection = 1;
myDropdown2.selection = 3;

//Buttons
var buttons = w.add ("group")
buttons.add ("button", undefined, "OK");
buttons.add ("button", undefined, "Cancel");

var a = w.show()
if(a == 2){
      exit(0);
        // Save UI User Settings
        var userChoice = {
        myDropdown1 : myDropdown1.selection,
        myDropdown2 : myDropdown2.selection,
        }
        app.insertLabel("usersettings", userChoice.toSource());
}