node.js - 使用 node.js 'util' 进行 promisify 会返回错误

Question

我试图在一个文件中创建一个函数来返回一个 promise ，我将从另一个文件中调用它。我正在尝试使用“util.promisify”来包装该函数，但出现错误。这是代码和错误:

来 self 的“checkEmail.js”:

const Profile = require('../../models/profile');
const util = require('util');


var exports = module.exports = {};

exports.findEmail = util.promisify(checkEmail());


 function checkEmail (email) {
   Profile.findOne({ 'emails': { $elemMatch: { email_address: email } } }, (err, userEmail) => {
    let conclusion = false;
    if (err) {
      console.log('Error in looking up an existing email');
    } else {
      if (userEmail) {
        console.log('We found an existing owner for email: ' + email);
        conclusion = true;
      }
    }
      return conclusion;
  })
 }

在“profile.js”上调用它:

router.route('/addemail/:id')

  // ADD EMAILS
  .put(function (req, res) {


    Profile.findOne({ 'owner_id': req.params.id }, function (err, profile) {
      if (err)
        res.send(err);

      EmailCheck.findEmail(req.body.email_address).then((data)=>{ 
        console.log('The answer is: ', data);
      });

      profile.emails.push({
        email_type: req.body.email_type,
        email_address: req.body.email_address
      })
      profile.save(function (err) {
        if (err)
          res.send(err);
        res.json(profile);
      });
    });
  });

我收到的错误是:

Config for: http://localhost:3000
internal/util.js:272
    throw new ERR_INVALID_ARG_TYPE('original', 'Function', original);

如有任何帮助，我们将不胜感激。

Answer 1

为了 Promisify，您传递给 util.promisify 的函数必须:

Take a function following the common error-first callback style, i.e. taking a (err, value) => callback as the last argument, and returns a version that returns promise

因此，您可以 promisify Profile.findOne，或者将回调作为最后一个参数传递给 checkEmail

function checkEmail (email, callback) {
   Profile.findOne({ 'emails': { $elemMatch: { email_address: email } } }, (err, userEmail) => {
    let conclusion = false;
    if (err)
      return callback(new Error('Error in looking up an existing email'));

    if (userEmail) {
      console.log('We found an existing owner for email: ' + email);
      conclusion = true;
    }
    return callback(null, conclusion);
  })
 }

然后你应该这样调用它:

exports.findEmail = util.promisify(checkEmail);

否则，您将把 checkEmail 的返回值传递给 .promisify，它不是遵循上面注释的样式的函数。