Function extractBeforeInputEvent

examples/simple/react.js:429–449

* Extract a SyntheticInputEvent for `beforeInput`, based on either native * `textInput` or fallback behavior. * * @param {string} topLevelType Record from `EventConstants`. * @param {DOMEventTarget} topLevelTarget The listening component root node. * @param {string} topLevelTargetID ID of `topL

(topLevelType, topLevelTarget, topLevelTargetID, nativeEvent, nativeEventTarget)

 * @return {?object} A SyntheticInputEvent.
 */
function extractBeforeInputEvent(topLevelType, topLevelTarget, topLevelTargetID, nativeEvent, nativeEventTarget) {
  var chars;

  if (canUseTextInputEvent) {
    chars = getNativeBeforeInputChars(topLevelType, nativeEvent);
  } else {
    chars = getFallbackBeforeInputChars(topLevelType, nativeEvent);
  }

  // If no characters are being inserted, no BeforeInput event should
  // be fired.
  if (!chars) {
    return null;
  }

  var event = SyntheticInputEvent.getPooled(eventTypes.beforeInput, topLevelTargetID, nativeEvent, nativeEventTarget);

  event.data = chars;
  EventPropagators.accumulateTwoPhaseDispatches(event);
  return event;
}

/**
 * Create an `onBeforeInput` event to match