anchor.diff:  #import('dart:html');
   
  -throttle(fn, delay) {
  +throttle(fn, int delay) {
     int handle = 0;
     return (args) {
       window.clearTimeout(handle);
  
positive.code:     }
    });
  
    document.on.click.add((event) {
    });
  
    document.on.click.add((event) {
    });
  
    document.on.touchStart.add((event) {
    });
  
    // rescale presentation when window is resized
  
negative.code:     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)) {
        event.preventDefault();
      }
    })
  
    // trigger impress action (next or prev) on keyup
    document.on.keyUp.add((event) {
      if (event.keyCode === 9 || (event.keyCode >= 32 && event.keyCode <= 34) || (event.keyCode >= 37 && event.keyCode <= 40)) {
        switch (event.keyCode) {
  