function cbFun() {
console.log("hello word!");
}
function asyncFun(callback) {
setTimeout(() => {
callback();
}, 3000);
}
 
asyncFun(cbFun);

function cbFun() {
console.log("hello word!");
}
function asyncFun() {
setTimeout(() => {
emitter.emit("msg");
}, 3000);
}
var emitter = new EventEmitter3();
emitter.on("msg", cbFun);
// 执行异步函数
asyncFun()

var PubSub = function() {
this.list = {};
};
//给订阅者提供订阅的方法
PubSub.prototype.subscribe = function(key, callback) {
if (!this.list[key]) {
this.list[key] = [];
}
this.list[key].push(callback);
};
//发布消息的功能
PubSub.prototype.publish = function(key, args) {
var fns = this.list[key];
// 如果没有订阅过该消息的话，则返回
if (!fns || fns.length === 0) {
return;
}
var len = fns.length;
while (len--) {
fns[len].apply(this, args);
}
};
// 取消订阅
PubSub.prototype.unsubscribe = function(key, fn) {
var fns = this.list[key];
if (!fns || fns.length === 0) {
return false;
}
if (!fn) {
fns && (fns.length = 0);
} else {
// 将fn删除
var len = fns.length;
while (len--) {
if (fns[len] === fn) {
fns.splice(len, 1);
}
}
}
};

var pubsub = new PubSub();
pubsub.subscribe("msg", cbFun);
function cbFun() {
console.log("hello word!");
}
function asyncFun() {
setTimeout(() => {
pubsub.publish("msg");
}, 3000);
}
asyncFun(); 

function cbFun() {
console.log("hello word!");
}
function asyncFun(callback) {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve();
}, 3000);
});
}
asyncFun().then(()=>{
cbFun()
}) 

function cbFun() {
console.log("hello word!");
}
function asyncFun() {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve();
}, 3000);
});
}
async function asyncFunArr() {
await asyncFun();
cbFun();
}
asyncFunArr();