es7终极异步方案demo

var sleep = (time)=> {
  return new Promise( (resolve, reject)=> {
    setTimeout(() =>{
      let flag=0
      if(flag==1){
        resolve();
      }else{
        reject()
      }

    }, time);
  })
};

var start = async  () =>{
  // 在这里使用起来就像同步代码那样直观
  try {
    console.log('start');
    await sleep(5000);
    console.log("5s")
    await sleep(3000)
    console.log('3s')
    console.log('end');
  }catch(e) {
    console.error("这是回掉错误")
  }

};

start();