Installation & Usage

First install the module via yarn or npm and do not forget to install the database driver as well:

$ yarn add mikro-orm mongodb # for mongo
$ yarn add mikro-orm mysql2  # for mysql
$ yarn add mikro-orm pg      # for postgresql
$ yarn add mikro-orm sqlite  # for sqlite

or

$ npm i -s mikro-orm mongodb # for mongo
$ npm i -s mikro-orm mysql2  # for mysql
$ npm i -s mikro-orm pg      # for postgresql
$ npm i -s mikro-orm sqlite  # for sqlite

Next you will need to enable support for decorators in tsconfig.json via:

"experimentalDecorators": true

Then call MikroORM.init as part of bootstrapping your app:

const orm = await MikroORM.init({
  entities: [Author, Book, BookTag],
  dbName: 'my-db-name',
  clientUrl: '...', // defaults to 'mongodb://localhost:27017' for mongodb driver
  autoFlush: false, // read more here: https://mikro-orm.io/unit-of-work/
});
console.log(orm.em); // access EntityManager via `em` property

You can also provide paths where you store your entities via entitiesDirs array. Internally it uses globby so you can use globbing patterns.

const orm = await MikroORM.init({
  entitiesDirs: ['./dist/app/**/entities'],
  // ...
});

You should provide list of directories, not paths to entities directly. If you want to do that instead, you should use entities array and use globby manually:

import { sync } from 'globby';

const orm = await MikroORM.init({
  entities: sync('./dist/app/**/entities/*.js').map(require),
  // ...
});

Entity discovery in TypeScript

Internally, MikroORM uses performs analysis of source files of entities to sniff types of all properties. This process can be slow if your project contains lots of files. To speed up the discovery process a bit, you can provide more accurate paths where your entity source files are:

const orm = await MikroORM.init({
  entitiesDirs: ['./dist/entities'], // path to your JS entities (dist), relative to `baseDir`
  entitiesDirsTs: ['./src/entities'], // path to your TS entities (source), relative to `baseDir`
  // ...
});

Request context

Then you will need to fork entity manager for each request so their identity maps will not collide. To do so, use the RequestContext helper:

const app = express();

app.use((req, res, next) => {
  RequestContext.create(orm.em, next);
});

More info about RequestContext is described here.

Now you can start defining your entities (in one of the entitiesDirs folders).