发布订阅

type eventType = string | symbol;
type eventListener = {
  once?: boolean;
  listener: Function;
};

type eventListType = Map<eventType, eventListener[]>;

interface EventEmitter {
  on(
    event: eventType,
    listener: eventListener['listener'],
    once: eventListener['once']
  ): () => void;
  off(event: eventType, listener: eventListener['listener']): void;
  emit(event: eventType, ...args: any[]): void;
  once(event: eventType, listener: eventListener['listener']): void;
}

class EventEmitter implements EventEmitter {
  private eventList: eventListType = new Map();
  on(event: eventType, listener: Function, once: boolean = false) {
    const eventWatchList = this.eventList.get(event);
    if (eventWatchList) {
      eventWatchList.push({
        listener,
        once,
      });
      this.eventList.set(event, eventWatchList);
    } else {
      this.eventList.set(event, [
        {
          listener,
          once,
        },
      ]);
    }

    return () => {
      this.off(event, listener);
    };
  }

  off(event: eventType, listener: Function) {
    const eventWatchList = this.eventList.get(event);
    if (!eventWatchList) return;
    this.eventList.set(
      event,
      eventWatchList.filter((item) => item.listener !== listener)
    );
  }

  emit(event: eventType, ...args: any[]): void {
    const eventWatchList = this.eventList.get(event);
    if (!eventWatchList) return;
    eventWatchList.forEach(({ listener, once }) => {
      listener(...args);
      once && this.off(event, listener);
    });
  }

  once(event: eventType, listener: Function) {
    this.on(event, listener, true);
  }
}

const emit = new EventEmitter();

class Person {
  constructor(public name: string) {}

  subscribe(type: string, handle: Function) {
    emit.on(type, handle.bind(this));
  }
  notify(type: string, handle: Function) {
    emit.emit(type, handle.call(this));
  }
}

const xm = new Person('xm');
const zs = new Person('zs');
const ls = new Person('ls');

xm.subscribe('eat', function (this: Person, ...args: any[]) {
  console.log(this.name, 'eat', ...args);
});

zs.subscribe('eat', function (this: Person, ...args: any[]) {
  console.log(this.name, 'eat', ...args);
});

xm.subscribe('eat', function (this: Person, ...args: any[]) {
  console.log(this.name, 'eat', ...args);
});

zs.notify('eat', function (this: Person) {
  return {
    name: this.name,
    see: '走出去玩',
  };
});