Mongoose, Typescript, Pre hook, hash password, compare passwords

user.ts

import * as mongoose from 'mongoose';
import {Schema} from 'mongoose';

const bcrypt = require('bcrypt-nodejs');

const userSchema = new Schema({
    local: {
        username: String,
        email: {type: String, unique: true, index: true, sparse: true, lowercase: true, trim: true},
        password: String,
        emailVerified: {type: Boolean, default: false}

    },
    google: {
        id: {type: String, unique: true, index: true, sparse: true},
        token: String,
        email: {type: String, unique: true},
        name: String
    }
});

userSchema.pre('save', function (next) {
    if (this.isModified('local.password')) {
        bcrypt.genSalt(10, (err, salt) => {
            if (err) {
                return next(err);
            }
            bcrypt.hash(this.local.password,
                salt, null, (error, hash) => {
                    if (error) {
                        return next(error);
                    }
                    this.local.password = hash;
                    return next(null, this);
                });
        });
    }
    return next(null, this);
});

userSchema.methods.comparePasswords = (candidatePassword, next) => {
    bcrypt.compare(candidatePassword, this.local.password, function (err, isMatch) {
        if (err) {
            return next(err);
        }
        next(null, isMatch);
    });
};


userSchema.methods.generateHash = function (password) {
    return bcrypt.hashSync(password, bcrypt.genSaltSync(8), null);
};

userSchema.methods.isPasswordValid = function (password) {
    return bcrypt.compareSync(password, this.local.password);
};

// Omit the password when returning a user
userSchema.set('toJSON', {
    transform: function (doc, ret) {
        delete ret.local.password;
        return ret;
    }
});

export const User = mongoose.model('User', userSchema);