手写EventBus

[Twlig]

手写EventBus：

class EventBus {
  constructor() {
    this.events = {};
  }
  on(event, fn) {
    if (this.events[event]) {
      this.events[event].push(fn);
    } else {
      this.events[event] = [fn];
    }
    return this;
  }
  emit(event, ...args) {
    if (this.events[event]) {
      this.events[event].forEach((fn) => {
        fn(...args);
      });
    }
    return this;
  }
  remove(event, fn) {
    if (!fn) {
      this.events[event] = null;
      return this;
    }
    if (this.events[event]) {
      const index = this.events[event].indexOf(fn);
      this.events[event].splice(index, 1);
    }
    return this;
  }
  once(event, fn) {
    const only = (...args) => {
      fn(...args);
      this.remove(event, only);
    };
    this.on(event, only);
    return this;
  }
}

const Lili = (text) => {
  console.log(`Lili: ${text}`);
};

const XiaoMing = (text) => {
  console.log(`XiaoMing: ${text}`);
};

const Amy = (city) => {
  console.log(`Amy: I come from ${city}`);
};

const eventBus = new EventBus();
eventBus.on("hi", Lili);
eventBus.on("hi", XiaoMing);
eventBus.once("city", Amy);

eventBus.emit("hi", "hello");
eventBus.remove("hi", Lili);
eventBus.emit("hi", "Where are you come from?");

eventBus.emit("city", "Beijing");
eventBus.emit("city", "Beijing");
/*
输出：
Lili: hello
XiaoMing: hello
XiaoMing: Where are you come from?
Amy: I come from Beijing
*/