example/dist/bundle.js
function getTargetInstForInputEventPolyfill(topLevelType, targetInst) {
  if (topLevelType === TOP_SELECTION_CHANGE || topLevelType === TOP_KEY_UP || topLevelType === TOP_KEY_DOWN) {
    // On the selectionchange event, the target is just document which isn't
    // helpful for us so just check activeElement instead.
    //
    // 99% of the time, keydown and keyup aren't necessary. IE8 fails to fire
    // propertychange on the first input event after setting `value` from a
    // script and fires only keydown, keypress, keyup. Catching keyup usually
    // gets it and catching keydown lets us fire an event for the first
    // keystroke if user does a key repeat (it'll be a little delayed: right
    // before the second keystroke). Other input methods (e.g., paste) seem to
    // fire selectionchange normally.
    return getInstIfValueChanged(activeElementInst);
  }
}
function getTargetInstForInputEventPolyfill(topLevelType, targetInst) {
  if (topLevelType === TOP_SELECTION_CHANGE || topLevelType === TOP_KEY_UP || topLevelType === TOP_KEY_DOWN) {
    // On the selectionchange event, the target is just document which isn't
    // helpful for us so just check activeElement instead.
    //
    // 99% of the time, keydown and keyup aren't necessary. IE8 fails to fire
    // propertychange on the first input event after setting `value` from a
    // script and fires only keydown, keypress, keyup. Catching keyup usually
    // gets it and catching keydown lets us fire an event for the first
    // keystroke if user does a key repeat (it'll be a little delayed: right
    // before the second keystroke). Other input methods (e.g., paste) seem to
    // fire selectionchange normally.
    return getInstIfValueChanged(activeElementInst);
  }
}
For IE8 and IE9.