// --- SET CURRENT APP VARIABLE NEEDED FOR DIALOGS & StandardAdditions.osax ---
var app = Application.currentApplication()
app.includeStandardAdditions = true
  
var MsgStr  = "This is an example of JXA Display Dialog"
var TitleStr  = "Dialog Title"
var AnswerStr = "NONE"

app.beep()
var oAns = app.displayDialog(MsgStr,
            {
              withTitle:      TitleStr
              ,withIcon:      "caution"
              ,buttons:       ["Cancel","OK"]
              ,defaultButton: "OK"
              ,cancelButton:  "Cancel"
            })

//--- Script is stopped here if user chooses "Cancel" ---

var BtnStr = oAns.buttonReturned

return ("Btn: " + BtnStr)