Mongoose the Typescript way...?

Trying to implement a Mongoose model in Typescript. Scouring the Google has revealed only a hybrid approach (combining JS and TS). How would one go about implementing the User class, on my rather naive approach, without the JS?

Want to be able to IUserModel without the baggage.

import {IUser} from './user.ts';
import {Document, Schema, Model} from 'mongoose';

// mixing in a couple of interfaces
interface IUserDocument extends IUser,  Document {}

// mongoose, why oh why '[String]' 
// TODO: investigate out why mongoose needs its own data types
let userSchema: Schema = new Schema({
  userName  : String,
  password  : String,
  firstName : String,
  lastName  : String,
  email     : String,
  activated : Boolean,
  roles     : [String]
});

// interface we want to code to?
export interface IUserModel extends Model<IUserDocument> {/* any custom methods here */}

// stumped here
export class User {
  constructor() {}
}

Here's how I do it:

export interface IUser extends mongoose.Document {
  name: string; 
  somethingElse?: number; 
};

export const UserSchema = new mongoose.Schema({
  name: {type:String, required: true},
  somethingElse: Number,
});

const User = mongoose.model<IUser>('User', UserSchema);
export default User;

Another alternative if you want to detach your type definitions and the database implementation.

import {IUser} from './user.ts';
import * as mongoose from 'mongoose';

type UserType = IUser & mongoose.Document;
const User = mongoose.model<UserType>('User', new mongoose.Schema({
    userName  : String,
    password  : String,
    /* etc */
}));

Inspiration from here: https://github.com/Appsilon/styleguide/wiki/mongoose-typescript-models

Most answers here repeat the fields in the TypeScript class/interface, and in the mongoose schema. Not having a single source of truth represents a maintenance risk, as the project becomes more complex and more developers work on it: fields are more likely to get out of sync. This is particularly bad when the class is in a different file vs. the mongoose schema.

To keep fields in sync, it makes sense to define them once. There are a few libraries that do this:

• typeodm.io - full test coverage, good examples, no traction yet
• mongoose-decorators-ts - best English, no traction yet
• typegoose - most popular, documentation needs improvement
• ts-mongoose - doesn't use decorators, second most popular, not actively maintained
• mongoose-schema-decorators - no traction yet
• mongoose-typescript - fork of typegoose

I haven't yet been fully convinced by any of them but typegoose seems actively maintained, and the developer accepted my PRs.

To think one step ahead: when you add a GraphQL schema into the mix, another layer of model duplication appears. One way to overcome this problem might be to generate TypeScript and mongoose code from the GraphQL schema.

Sorry for necroposting but this can be still interesting for someone. I think Typegoose provides more modern and elegant way to define models

Here is an example from the docs:

import { prop, Typegoose, ModelType, InstanceType } from 'typegoose';
import * as mongoose from 'mongoose';

mongoose.connect('mongodb://localhost:27017/test');

class User extends Typegoose {
    @prop()
    name?: string;
}

const UserModel = new User().getModelForClass(User);

// UserModel is a regular Mongoose Model with correct types
(async () => {
    const u = new UserModel({ name: 'JohnDoe' });
    await u.save();
    const user = await UserModel.findOne();

    // prints { _id: 59218f686409d670a97e53e0, name: 'JohnDoe', __v: 0 }
    console.log(user);
})();

For an existing connection scenario, you can use as the following (which may be more likely in the real situations and uncovered in the docs):

import { prop, Typegoose, ModelType, InstanceType } from 'typegoose';
import * as mongoose from 'mongoose';

const conn = mongoose.createConnection('mongodb://localhost:27017/test');

class User extends Typegoose {
    @prop()
    name?: string;
}

// Notice that the collection name will be 'users':
const UserModel = new User().getModelForClass(User, {existingConnection: conn});

// UserModel is a regular Mongoose Model with correct types
(async () => {
    const u = new UserModel({ name: 'JohnDoe' });
    await u.save();
    const user = await UserModel.findOne();

    // prints { _id: 59218f686409d670a97e53e0, name: 'JohnDoe', __v: 0 }
    console.log(user);
})();

Try ts-mongoose. It uses conditional types to do the mapping.

import { createSchema, Type, typedModel } from 'ts-mongoose';

const UserSchema = createSchema({
  username: Type.string(),
  email: Type.string(),
});

const User = typedModel('User', UserSchema);