If you require some logic to run each time the widget appears on the page, add the beforeAppear() function to the widget JavaScript’s return object:

beforeAppear: function(page) {
  // Code to run before showing the widget here.
}

beforeAppear() is run once any re-population of mapping data has occurred. This can be useful when a Web API call is required every time the widget is shown, or, some other functionality required every time the widget is shown.