anchor.diff:              (target !== document.documentElement))) {
         target = target.parentNode;
       }
  -    if (api.goto(target)) {
  +    if (api.goto(target) != null) {
         event.preventDefault();
       }
     });
  
positive.code:   };
  }
  
  main() {
    document.on.change.add((event) {
      var api = event.detail.api;
    });
  
    // prevent default keydown action when one of supported key is pressed
    document.on.keyDown.add((event) {
      if (event.keyCode === 9 || (event.keyCode >= 32 && event.keyCode <= 34 ) || (event.keyCode >= 37 && event.keyCode <= 40)) {
  
negative.code:       }
      }
  
      if (api.goto(target) != null) {
        event.stopImmediatePropagation();
        event.preventDefault();
      }
  