发布订阅模式

粗糙版

function Event() {
  this.callbacks = [];
  this.result = [];
}

Event.prototype.on = function(callback) {
  this.callbacks.push(callback);
};

Event.prototype.emit = function(data) {
  this.result.push(data);
  this.callbacks.forEach(c => {
    c(this.result);
  });
};

const e = new Event();

e.on((e)=>console.log(e))
e.on(()=>console.log('done'))

e.emit('haha')
e.emit('hello')

改进版

function Event() {
  this.events = {};
}

Event.prototype.on = function(eventName, fn) {
  if (!this.events[eventName]) {
    this.events[eventName] = [];
  }
  this.events[eventName].push(fn);
};

Event.prototype.emit = function(eventName, data) {
  if (this.events[eventName]) {
    this.events[eventName].forEach(fn => fn(data));
  }
};

const e = new Event();

e.on("phone", e => console.log(e));
e.on("phone", () => console.log("end"));

e.emit("phone", "喂");
e.emit("phone", "吃了吗");