订阅发布

class myEventEmit {
  constructor() {
    this.events = {};
  }
  on(type, handler) {
    if (!(handler instanceof Function)) {
      throw new Error('handler 必须是一个函数');
    }
    if (type in this.events) {
      this.events[type].push(handler);
    } else {
      this.events[type] = [handler];
    }
  }

  emit(type, params) {
    if (type in this.events) {
      this.events[type].forEach(handler => {
        handler(params);
      });
    }
  }

  off(type, handler) {
    if (type in this.events) {
      this.events[type].splice(this.events[type].indexOf(handler), 1);
    }
  }
}

// 测试代码
let ef = new myEventEmit();

const type = 'type1';
const a1 = params => console.log(1, params);
const a2 = params => console.log(2, params);
const a3 = params => console.log(3, params);

// 添加订阅
ef.on(type, a1);
ef.on(type, a2);
ef.on(type, a3);

// 发布订阅
ef.emit(type, 'old');

setTimeout(() => {
  // 移除订阅
  ef.off(type, a1);
  ef.off(type, a3);
  // 发布订阅
  ef.emit(type, 'new');
}, 2000);