发布者和订阅者完全解耦（通过消息队列进行通信）

适用场景：功能模块间进行通信，如Vue的事件总线。
ES6实现方式：

class eventManager {constructor() {this.eventList = {};}on(eventName, callback) {if (this.eventList[eventName]) {this.eventList[eventName].push(callback);} else {this.eventList[eventName] = [callback];}}fire(eventName, data) {if (eventName in this.eventList &&Array.isArray(this.eventList[eventName])) {this.eventList[eventName].forEach(callback => callback(data));} else {console.log(`${eventName} is not a resgisted event`);}}off(eventName, callback) {if (callback) {if (eventName in this.eventList &&Array.isArray(this.eventList[eventName])) {let index = this.eventList[eventName].indexOf(callback);index > -1 && this.eventList[eventName].splice(index, 1);} else {console.log(`${eventName} has not been listen`);}} else {delete this.eventList[eventName]}}
}
let eventManager1 = new eventManager();
eventManager1.on("event", data => {console.log(data);
});
eventManager1.fire("event", "haha");
eventManager1.off("event");