CODEWITHSUNDEEP
node.jsexpressmongoose
Charles Adorty
Charles Adorty

Reputation: 3

Variable cannot be change inside findOne

I want to make a quick Util file which would contain multiple functions such as an user_id to his name. As the image under shows, I tried to save the value throughout the code but the variable "name" doesn't get affected inside the .then(user => {}) for some reasons

I tried returning directly the value without using variable to save it. I debugged and code runs fine and it gets into the if(!user){}else{}perfectly. The user returned by Mongoose works and I can console log the user.username (Cannot return it, either can I save it to a variable, which is what i'm doing on the code under)

const User = require('../models/users')

exports.id2name = (id) => {
  let name = 'none'
  User.findOne({_id: id}).then(user => {
    if (!user) {
      name = 'Unknown'
    } else {
      name = user.username
    }
  }).catch(err => console.log(err))
  return name
}

I don't get any errors on my console. It is returning 'none' as a result even if it gets into the else statement inside the mongoose request.

Upvotes: 0

Views: 124

Answers (2)

Md Alamin
Md Alamin

Reputation: 1462

You are getting this result for asynchronous behaviours of JavaScript.

You can try this code for getting the desired result.

exports.id2name = async (id) => {
 try{
   let name = 'none'

   const user = await User.findOne({_id: id});
   if(user) {
     name = user.username;
   } else {
     name = 'Unknown';
   }
  return name;
 } catch(e) {
   console.log(e);
 }
}

Upvotes: 2

Lellansin
Lellansin

Reputation: 912

It's asynchronous return. I mean you may need to use callback, Promise or other asynchronous way to deal with it, for example:

const User = require('../models/users')

exports.id2name = (id, callback) => {
  User.findOne({_id: id}).then(user => {
    if (!user) {
      callback(null, 'Unknown')
    } else {
      callback(null, user.username)
    }
  }).catch(callback)
}

or promise:

const User = require('../models/users')

exports.id2name = (id) => {
  return new Promise((resolve, reject) => {
    User.findOne({_id: id}).then(user => {
      if (!user) {
        resolve('Unknown')
      } else {
        resolve(user.username)
      }
    }).catch(reject);
  });
}

Upvotes: 1

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