详解koa2学习中使用 async 、await、promise解决异步的问题

let asyncFn = async（）=> {
 let data = null;
 data = await getData(url);//getData()返回的数据是 {name:'my name is data!'}
 console.log(data.name);//打印出的是my name is data! 
}

let notAsyncFn =（）=> {
 let data = null;
 data = getData(url);//getData()返回的数据是 {name:'my name is data!'}
 console.log(data.name);//打印出的是undefined; 因为data此时还是null;
}

var getData = function (url){
  console.log("get start");
  console.log(url);
  return new Promise(function (resolve, reject) {
//下面的request()方法 是nodeJS的request模块；
   request(url, function (error, response, body) {
    if (!error && response.statusCode == 200) {
     resolve(response.body);
    }else{
     //throw new Error(response.statusText)
     reject('===error===');
    }
   });

  })

  console.log("get end");

 }

/**
 * koa2路由代码
 */
//引入router模块
var router = require('koa-router')();
//引入server模块 封装的请求函数
var server = require('../server');
//url 是假的额 写的百度的网址
const url = 'www.baidu.com';

router.get('/',async function (ctx,next){
 var data = await server.get(url);
 console.log('======data=====');
 console.log(data);
 await ctx.render('myPage',{
  title: '123wangcong',
  data: data
 })
});
module.exports = router;

/**
 * server模块的代码
 */
node的request模块
var request = require('request');
module.exports = {
 get : function (url){
  console.log("get start");
  console.log(url);
  return new Promise(function (resolve, reject) {
   request(url, function (error, response, body) {
    if (!error && response.statusCode == 200) {
     resolve(response.body);
    }else{
     //throw new Error(response.statusText)
     reject('error===');
    }
   });

  })
  console.log("get end");
 }
}

{
 "name": "koa2-demo",
 "version": "0.1.0",
 "scripts": {
 "start": "NODE_ENV=development ./node_modules/.bin/nodemon bin/run",
 "test1": "NODE_ENV=test ./node_modules/.bin/nodemon bin/run",
 "koa": "./node_modules/.bin/runkoa bin/www",
 "pm2": "pm2 start bin/run ",
 "test": "./node_modules/.bin/mocha -u bdd"
 },
 "dependencies": {
 "co": "^4.6.0",
 "debug": "^2.2.0",
 "ejs": "^2.5.6",
 "jade": "~1.11.0",
 "koa": "^2.0.0",
 "koa-bodyparser": "^2.0.1",
 "koa-convert": "^1.2.0",
 "koa-json": "^1.1.1",
 "koa-logger": "^1.3.0",
 "koa-onerror": "^1.2.1",
 "koa-request": "^1.0.0",
 "koa-router": "^7.0.0",
 "koa-static": "^1.5.2",
 "koa-views": "^5.0.1",
 "runkoa": "^1.5.2"
 },
 "devDependencies": {
 "mocha": "^2.4.5",
 "nodemon": "^1.9.1",
 "should": "^8.3.0",
 "supertest": "^1.2.0"
 }
}