javascript - Node js，函数不等待响应

Question

我是Node js的新手。
从逻辑上讲，await应该等待函数完成，然后下一行代码应该运行，但是在我的函数中，即使使用await之后，它也不等待进程(2)完成。我想念什么？

const getDefaultTemplates = async (token) => {
  const emailertoken = process.env.EMAILER_AUTH_TOKEN;
  const key = 'defaultTemplates';
  // This should run first
  console.log('hi');
  let defaultTemplatesVar = '';
  let fromCache = 0;

  // This should run second. Need response from redisClient to return parent function
  const defaultTemplates = await redisClient.get(key, (err, data) => {
    if (err) {
      console.log(err);
    }
    // If data is found in cache
    if (data != null) {
      console.log('from cache');
      defaultTemplatesVar = JSON.parse(data);
      fromCache = 1;
      console.log('defaultTemplatesVar1 = ', defaultTemplatesVar);
    }
    return defaultTemplatesVar;
  });

  console.log('defaultTemplatesVar2 = ', defaultTemplatesVar);
  console.log('fromCache = ', fromCache);
  if (fromCache === 0) {
    // If data is not found in cache, call api
    // console.log('from api');
    try {
      const response = await axios.get(`${process.env.EMAILER_API_URL}/get-system-templates`, {
        headers: {
          Authorization: `bearer ${emailertoken}`,
        },
      });
      console.log('from data');
      redisClient.setex(key, 3600, JSON.stringify(response.data._embedded.get_system_templates));
      defaultTemplatesVar = response.data._embedded.get_system_templates;
      console.log('defaultTemplatesVar3 = ', defaultTemplatesVar);
    } catch (error) {
      console.error(error);
    }
  }

  // This should run at last, to return value to parent function getDefaultTemplates()
  console.log('bye');
  console.log('defaultTemplatesVar4 = ', defaultTemplatesVar);
  return defaultTemplates;
};

输出->

hi
defaultTemplatesVar2 =  
fromCache =  0
from cache
defaultTemplatesVar1 =  [ { name: 'versafix-1', description: 'The versatile template' },
  { name: 'givecentral', description: 'The Givecentral Template' } ]
from data
defaultTemplatesVar3 =  [ { name: 'versafix-1', description: 'The versatile template' },
  { name: 'givecentral', description: 'The Givecentral Template' } ]
bye
defaultTemplatesVar4 =  [ { name: 'versafix-1', description: 'The versatile template' },
  { name: 'givecentral', description: 'The Givecentral Template' } ]

输出应为1,2,3,4的串联。

Answer 1

回调函数不能为await，
要将回调fn转换为Promise fn，请检查https://www.npmjs.com/package/redis#promises。
如果您使用的是其他软件包，则实际上可以通过

const redisGet = (key) => new Promise((resolve, reject) => {
  redisClient.get(key, (err, data) => {
    if (err) return reject(err);
    return resolve(data);
  });
});

// So you can do
const data = await redisGet(key);
// or
redisGet(key).then((data) => { ... }).catch((err) => { ... });

所以你应该怎么做

try {
  ...

  const data = await redisClient.get(key);

  if (data != null) {
    console.log('from cache');
    defaultTemplatesVar = JSON.parse(data);
    fromCache = 1;
    console.log('defaultTemplatesVar1 = ', defaultTemplatesVar);
  }
  const defaultTemplates = defaultTemplatesVar;
  ...
} catch (err) {
  console.error(err);
}

关于Callback vs Promise的简单教程