javascript 异步实现方案

1、回调函数

　　fn1( fn2 );

2、事件监听

fn1.on('done', fn2);

function fn1() {
  setTimeout(function(){
       fn1.trigger('done');
    },1000)
}

3、发布-订阅

（1）fn2像“信号中心”订阅了done信号
        Jquery.subscribe("done", fn2);

(2) fn1向信号中心发布信号
    function fn1(){
        setTimeout(function(){
             Jquery.publish("done");
        },2000)
    }

4、 promises

fn1().then(fn2);

function fn1(){
  var dfd = $.Deferred();
  setTimeout(function(){
     resolve();
  },2000);
}

5、generator

var fetch = require('node-fetch');

function * gen(){
     var url = "xxxxx.github";
     var result = yelid fetch(url);
    console.log(result.do);
}

var g = gen();
var result = g.next();

result.value.then(function(data){
   return data.json();
}).then(function(data){
    g,next(data)
})

6、 async 函数

async function getStockPriceByName(name) {
  var symbol = await getStockSymbol(name);
  var stockPrice = await getStockPrice(symbol);
  return stockPrice;
}

getStockPriceByName('goog').then(function (result) {
  console.log(result);
});