Promise {<pending>} of bcrypt inside promise-CodePudding

I have a lambda function that is connected to Mongo via mongoose. The user inputs a name and password on the frontend and the lambda function searches whether the user exists and afterwards the crypted password is compared via bcrypt.

Right now bcrypt gives me {<promise pending>}, when I console.log(match).

However, I can't simply add an await as the check is inside a promise.

require("dotenv").config();
const mongoose = require("mongoose");
const User = require('../server/models/user');
const bcrypt = require('bcryptjs')

exports.handler = async (event, context) => {
  context.callbackWaitsForEmptyEventLoop = false;
  
  mongoose.connect(`${process.env.MONGO_URI}`,{
    useNewUrlParser: true,
    useUnifiedTopology: true,
  }
  );
  
  let {name, password} = JSON.parse(event.body);

 let fd = await new Promise((res,rej)=>User.findOne(
    {
      name:name,
    },
    (err, user) => {
      if (err) {
        rej({
          statusCode: 500,
          body: JSON.stringify({ msg: err.message }),
        });
      } else {
    //==>    const match = await bcrypt.compare(password, JSON.stringify(user.password)); 

 
        if (match) {
        let statusCode = user && match? 200:405
        res({
          statusCode,
          headers: {
            "Access-Control-Allow-Origin": "*", 
            "Content-Type": "application/json",
          },
          body: JSON.stringify({ user}),
        });
      }
      }
    }
  ));
  return fd
};

So basically how can I 'await' bcrypt in that case or how could I write this function in another way? Thanks for reading!

CodePudding user response：

You cannot use await there, because the callback in which it occurs is not an async function.

However, you should better use the promise you can get from findOne:

exports.handler = async (event, context) => {
  context.callbackWaitsForEmptyEventLoop = false;
  
  mongoose.connect(process.env.MONGO_URI, {
    useNewUrlParser: true,
    useUnifiedTopology: true,
  });
  
  const {name, password} = JSON.parse(event.body);
  const user = await User.findOne({name}).exec();
  const match = user && await bcrypt.compare(password, JSON.stringify(user.password)); 
  if (!match) {
    throw {
      statusCode: 405,
      body: "Invalid user or password",
    }
  }
  return {
    statusCode: 200,
    headers: {
      "Access-Control-Allow-Origin": "*", 
      "Content-Type": "application/json",
    },
    body: JSON.stringify({ user}),
  };
};

CodePudding user response：

you could chain the function inside the promise:

let fd = await new Promise((res, rej) =>
  User.findOne(
    {
      name: name,
    },
    (err, user) => {
      if (err) {
        rej({
          statusCode: 500,
          body: JSON.stringify({ msg: err.message }),
        });
      } else {
        bcrypt
          .compare(password, JSON.stringify(user.password))
          .then((match) => {
            if (match) {
              let statusCode = user && match ? 200 : 405;
              res({
                statusCode,
                headers: {
                  "Access-Control-Allow-Origin": "*",
                  "Content-Type": "application/json",
                },
                body: JSON.stringify({ user }),
              });
            }
          });
      }
    }
  )
);