Mongoose Methods and Typescript - this property is undefined

Question

I'm developing a typescript app a restful api using node,express and mongoose.

I have an auth controller with a store function attached to POST: /api/auth . The user passes in their email and password to compare it against the hashed version.

However the comparePassword function in the use.model.ts doesent work because this.password is undefined.

auth.controller.ts

import { Request, Response, NextFunction } from 'express';

import User from './../users/user.model';
import jwt from 'jsonwebtoken';
import Config from './../../config/config';

class AuthController {

    private config: any;

    constructor() {

        this.config = new Config();

    }

    public async store(req: Request, res: Response): Promise<any> {

        const input = req.body;

        console.log(input);
        try {

            let user = await User.findOne({ 'email': input.email });

            if (!user) {
                throw {};
            }
            console.log(user);

            user.schema.methods.comparePassword(input.password, (err: any, isMatch: any) => {

                if (err || !isMatch) {

                    return res.status(401).json({
                        success: false,
                        status: 401,
                        data: { err, isMatch },
                        message: 'Authentication Failed, wrong password',
                    });

                }

                if (!err && isMatch) {

                    const token = jwt.sign({ sub: user._id }, this.config.jwt.secretOrKey);

                    return res.status(200).json({
                        success: true,
                        status: 200,
                        data: { user, token },
                        message: 'Authentication Successful',
                    })

                }


            })

        } catch (err) {

            return res.status(404).json({
                success: false,
                status: 404,
                data: err,
                message: 'Failed to Authenticate'
            })

        }


    }
}

export default AuthController;

user.model.ts

import { Schema, Model, Document, model } from 'mongoose';
import bcrypt from 'bcryptjs';
import { UserInterface } from './user.interface';


const UserSchema = new Schema({

    email: {
        type: String,
        required: true
    },
    password: {
        type: String,
        required: true
    },

}, {
        timestamps: { createdAt: 'created_at', updatedAt: 'updated_at' },
    });


UserSchema.pre('save', function (next) {
    let user = <UserInterface>this;
    let SALT_WORK_FACTOR = 10;

    // only hash the password if it has been modified (or is new)
    if (!user.isModified('password')) return next();

    // generate a salt
    bcrypt.genSalt(SALT_WORK_FACTOR, function (err, salt) {
        if (err) return next(err);

        // hash the password using our new salt
        bcrypt.hash(user.password, salt, function (err, hash) {
            if (err) return next(err);

            // override the cleartext password with the hashed one
            user.password = hash;
            next();
        });
    });
});

UserSchema.methods.comparePassword = function (candidatePassword: any, cb: any) {

    //let user = <UserInterface>this;

    console.log(candidatePassword);
    console.log(this.password);

    bcrypt.compare(candidatePassword, this.password, function (err, isMatch) {
        if (err) return cb(err);
        cb(null, isMatch);
    });
};



const User = model<UserInterface>('Users', UserSchema);

export default User;

I have similar comparePassword function working in another project that doesn't use typescript. So im not sure why "this" is undefined and is not set to the mongoose user object.

Answer 1

Here's what I do to bypass that typescript issue.

const self:any = this;

Usage example:

UserSchema.methods.comparePassword = function (candidatePassword: any, cb: any) {
    const self:any = this;

    console.log(candidatePassword);
    console.log(self.password);

    bcrypt.compare(candidatePassword, self.password, function (err, isMatch) {
        if (err) return cb(err);
        cb(null, isMatch);
    });
};

Also if you're in a rush and don't want to create an interface you can do this on your pre events.

UserSchema.pre<any>('save', function(next) {
   if (!this.isModified('password')) 
       return next();
   ...
})