docs: function onClick(event) {
      if (Date.now() - lastPreventedTime > PREVENT_DURATION) {
        return; // Too old.
      }
  
      var touches = event.touches && event.touches.length ? event.touches : [event];
      var x = touches[0].clientX;
      var y = touches[0].clientY;
      // Work around desktop Webkit quirk where clicking a label will fire two clicks (on the label
      // and on the input element). Depending on the exact browser, this second click we don't want
      // to bust has either (0,0), negative coordinates, or coordinates equal to triggering label
      // click event
      if (x < 1 && y < 1) {
        return; // offscreen
      }
      if (lastLabelClickCoordinates &&
          lastLabelClickCoordinates[0] === x && lastLabelClickCoordinates[1] === y) {
        return; // input click triggered by label click
      }
      // reset label click coordinates on first subsequent click
      if (lastLabelClickCoordinates) {
        lastLabelClickCoordinates = null;
      }
      // remember label click coordinates to prevent click busting of trigger click event on input
      if (event.target.tagName.toLowerCase() === 'label') {
        lastLabelClickCoordinates = [x, y];
      }
  
      // Look for an allowable region containing this click.
      // If we find one, that means it was created by touchstart and not removed by
      // preventGhostClick, so we don't bust it.
      if (checkAllowableRegions(touchCoordinates, x, y)) {
        return;
      }
  
      // If we didn't find an allowable region, bust the click.
      event.stopPropagation();
      event.preventDefault();
  
      // Blur focused form elements
      event.target && event.target.blur();
    }