详解node Async/Await 更好的异步编程解决方案

var sleep = function (time) {
  return new Promise(function (resolve, reject) {
    setTimeout(function () {
      resolve();
    }, time);
  })
};

var start = async function () {
  // 在这里使用起来就像同步代码那样直观
  console.log('start');
  await sleep(3000);
  console.log('end');
};

start();

async function dbFuc(db) {
 let docs = [{}, {}, {}];

 // 报错
 docs.forEach(function (doc) {
  await db.post(doc);
 });
}

var sleep = function (time) {
  return new Promise(function (resolve, reject) {
    setTimeout(function () {
      // 返回 ‘ok'
      resolve('ok');
    }, time);
  })
};

var start = async function () {
  let result = await sleep(3000);
  console.log(result); // 收到 ‘ok'
};

async function dbFuc(db) {
 let docs = [{}, {}, {}];

 // 可能得到错误结果
 docs.forEach(async function (doc) {
  await db.post(doc);
 });
}

async function dbFuc(db) {
 let docs = [{}, {}, {}];
 let promises = docs.map((doc) => db.post(doc));

 let results = await Promise.all(promises);
 console.log(results);
}

var sleep = function (time) {
  return new Promise(function (resolve, reject) {
    setTimeout(function () {
      // 模拟出错了，返回 ‘error'
      reject('error');
    }, time);
  })
};

var start = async function () {
  try {
    console.log('start');
    await sleep(3000); // 这里得到了一个返回错误
    
    // 所以以下代码不会被执行了
    console.log('end');
  } catch (err) {
    console.log(err); // 这里捕捉到错误 `error`
  }
};