我如何使這個功能成為現實？

Question

我正在使用快遞路線

app.get('/api/users/:username', (req, res) => {
  let username = req.params.username;
  findUserInApi(username)
    .then(foundUser => {
      if (foundUser) {
        res.status(403).send('User not found in api yet');
      }else{
        res.json(foundUser);
      }
    });
});

我希望findUserInApi是一個承諾，因為我需要等待該函數內部發生的提取。

這是findUserInApi

const findUserInApi = (username) => {
  findChattersPerRole()
    .then(chattersPerRole => {
      console.log(`${username} should\'ve been added by now...`);
      //console.log(chattersPerRole);
      let wantedUser = find(chattersPerRole, {username});
      if (!wantedUser) {
        console.log(`${wantedUser} wasn't found m8`);
        return Promise.resolve(null);
      }
      console.log('wanteduser is: ', wantedUser);
      getUserByUsername(wantedUser.username)
        .then(foundUser => {
          console.log('founduser is: ', foundUser);
          return Promise.resolve(foundUser);
        });
    });
};

我以前只在找不到時返回null，而在發現他時僅返回foundUser，但是我試圖通過返回Promise.resolve來做出承諾。 我不確定如何解決此問題...

Answer 1

您需要返回整個承諾鏈，如下所示：

const findUserInApi = (username) => {
  return findChattersPerRole()
    .then(chattersPerRole => {
      console.log(`${username} should\'ve been added by now...`);
      //console.log(chattersPerRole);
      let wantedUser = find(chattersPerRole, {username});
      if (!wantedUser) {
        console.log(`${wantedUser} wasn't found m8`);
        return Promise.resolve(null);
      }
      console.log('wanteduser is: ', wantedUser);
      getUserByUsername(wantedUser.username)
        .then(foundUser => {
          console.log('founduser is: ', foundUser);
          return Promise.resolve(foundUser);
        });
    });
};

請注意，在return findChattersPerRole().then()添加了return 。

但是，您正在嵌套承諾鏈。 那是一種反模式。 另外，如評論中所述，您無需在Promise.resolve()中使用Promise.resolve() .then() ，它會自動應用。 您的代碼可以重組為如下形式：

const findUserInApi = (username) => {
  return findChattersPerRole()
    .then(chattersPerRole => {
      console.log(`${username} should\'ve been added by now...`);
      //console.log(chattersPerRole);
      return find(chattersPerRole, {username});
    })
    .then(wantedUser => {
      if (wantedUser) {
        console.log('wanteduser is: ', wantedUser);
        return getUserByUsername(wantedUser.username);
      }
      else console.log(`${wantedUser} wasn't found m8`);
    })
    .then(foundUser => {
      if (foundUser) console.log('founduser is: ', foundUser);
      return foundUser;
    });
};