react 源码解析 18 事件系统

export default class Demo13 extends React.Component {  state = { show: false };  componentDidMount() {    document.addEventListener("click", () => {      this.setState({ show: false });    });  }  handleClick = (e) => {    e.stopPropagation();//react17中生效    // e.nativeEvent.stopImmediatePropagation(); //react16中生效 stopImmediatePropagation也阻止本级监听函数执行    this.setState({ show: true });  };  render() {    return (      <div>        <button onClick={this.handleClick}>显示</button>        {this.state.show && <div onClick={(e) => e.nativeEvent.stopImmediatePropagation()}>modal</div>}      </div>    );  }}

   //DOMPluginEventSystem.js   SimpleEventPlugin.registerEvents();

   function registerSimpleEvents() {     registerSimplePluginEventsAndSetTheirPriorities(discreteEventPairsForSimpleEventPlugin, DiscreteEvent);     //...   }      function registerSimplePluginEventsAndSetTheirPriorities(eventTypes, priority) {     for (var i = 0; i < eventTypes.length; i += 2) {       var topEvent = eventTypes[i];       var event = eventTypes[i + 1];       var capitalizedEvent = event[0].toUpperCase() + event.slice(1);       var reactName = 'on' + capitalizedEvent;       eventPriorities.set(topEvent, priority);       topLevelEventsToReactNames.set(topEvent, reactName);       registerTwoPhaseEvent(reactName, [topEvent]);//注册捕获和冒泡两个阶段的事件     }   }

   function registerTwoPhaseEvent(registrationName, dependencies) {     registerDirectEvent(registrationName, dependencies);     registerDirectEvent(registrationName + 'Capture', dependencies);   }

   function registerDirectEvent(registrationName, dependencies) {    //...        for (var i = 0; i < dependencies.length; i++) {       allNativeEvents.add(dependencies[i]);//生成allNativeEvents对象     }   }

   //由函数createRootImpl调用，也就是在创建根节点之后执行   function listenToAllSupportedEvents(rootContainerElement) {       allNativeEvents.forEach(function (domEventName) {         if (!nonDelegatedEvents.has(domEventName)) {           listenToNativeEvent(domEventName, false, rootContainerElement, null);         }            listenToNativeEvent(domEventName, true, rootContainerElement, null);       });     }   }

   function listenToNativeEvent(domEventName, isCapturePhaseListener, rootContainerElement, targetElement) {    //...        if (!listenerSet.has(listenerSetKey)) {       if (isCapturePhaseListener) {         eventSystemFlags |= IS_CAPTURE_PHASE;       }          addTrappedEventListener(target, domEventName, eventSystemFlags, isCapturePhaseListener);       listenerSet.add(listenerSetKey);     }   }

   function addTrappedEventListener(targetContainer, domEventName, eventSystemFlags, isCapturePhaseListener, isDeferredListenerForLegacyFBSupport) {     //创建具有优先级的监听函数     var listener = createEventListenerWrapperWithPriority(targetContainer, domEventName, eventSystemFlags);      //...     targetContainer =  targetContainer;     var unsubscribeListener;         if (isCapturePhaseListener) {//节点上添加事件       if (isPassiveListener !== undefined) {         unsubscribeListener = addEventCaptureListenerWithPassiveFlag(targetContainer, domEventName, listener, isPassiveListener);       } else {         unsubscribeListener = addEventCaptureListener(targetContainer, domEventName, listener);       }     } else {       if (isPassiveListener !== undefined) {         unsubscribeListener = addEventBubbleListenerWithPassiveFlag(targetContainer, domEventName, listener, isPassiveListener);       } else {         unsubscribeListener = addEventBubbleListener(targetContainer, domEventName, listener);       }     }   }

   function createEventListenerWrapperWithPriority(targetContainer, domEventName, eventSystemFlags) {     var eventPriority = getEventPriorityForPluginSystem(domEventName);     var listenerWrapper;        switch (eventPriority) {       case DiscreteEvent:         listenerWrapper = dispatchDiscreteEvent;         break;          case UserBlockingEvent:         listenerWrapper = dispatchUserBlockingUpdate;         break;          case ContinuousEvent:       default:         listenerWrapper = dispatchEvent;         break;     }     //绑定dispatchDiscreteEvent     return listenerWrapper.bind(null, domEventName, eventSystemFlags, targetContainer);   }

   function dispatchDiscreteEvent(domEventName, eventSystemFlags, container, nativeEvent) {     {       flushDiscreteUpdatesIfNeeded(nativeEvent.timeStamp);     }        discreteUpdates(dispatchEvent, domEventName, eventSystemFlags, container, nativeEvent);   }

   function unstable_runWithPriority(priorityLevel, eventHandler) {//eventHandler就是dispatchEvent函数     switch (priorityLevel) {       case ImmediatePriority:       case UserBlockingPriority:       case NormalPriority:       case LowPriority:       case IdlePriority:         break;          default:         priorityLevel = NormalPriority;     }        var previousPriorityLevel = currentPriorityLevel;     currentPriorityLevel = priorityLevel;        try {       return eventHandler();     } finally {       currentPriorityLevel = previousPriorityLevel;     }   }

   function batchedEventUpdates(fn, a, b) {     if (isBatchingEventUpdates) {       return fn(a, b);     }        isBatchingEventUpdates = true;        try {       return batchedEventUpdatesImpl(fn, a, b);       //fn参数即：       //function () {       //  return dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent,                 //ancestorInst);       //}       function () {       return dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, ancestorInst);     }     } finally {       isBatchingEventUpdates = false;       finishEventHandler();     }   }

   function dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, targetInst, targetContainer) {     var nativeEventTarget = getEventTarget(nativeEvent);     var dispatchQueue = [];     //extractEvent生成SyntheticEvent     extractEvents(dispatchQueue, domEventName, targetInst, nativeEvent, nativeEventTarget, eventSystemFlags);     //processDispatchQueue执行形成事件队列     processDispatchQueue(dispatchQueue, eventSystemFlags);   }