TypeORM

TypeORM is an open-source object-relational mapper (ORM) for TypeScript and JavaScript that runs in Node.js and, in some configurations, in the browser. It provides both Active Record and Data Mapper patterns, allowing developers to work with database records as class instances while offering repositories and a query builder for more control.

The project supports a range of relational databases, including MySQL, PostgreSQL, MariaDB, SQLite, Microsoft SQL Server, Oracle, and SAP HANA, as well as MongoDB through a dedicated integration. TypeORM uses decorators to map classes to database tables, with entities, columns, relations, and indices defined in code. It emphasizes a strong TypeScript experience, including type safety and IntelliSense.

Core concepts include entities, repositories, an entity manager or data source, and a query builder. In Active Record mode, entity classes can include persistence methods; in Data Mapper mode, a separate repository handles data access. DataSource (formerly a Connection) encapsulates database connections and configuration and is central to setup and lifecycle management.

Key features include migrations and schema synchronization, support for lazy and eager relations, cascades, and transactions, as well as event-based subscribers. Relationship mappings cover OneToOne, OneToMany, ManyToOne, and ManyToMany. The library also provides caching options, custom naming strategies, and logging facilities to aid debugging and performance tuning.

Usage and ecosystem: TypeORM works with TypeScript and JavaScript projects and is commonly used with frameworks such as NestJS. It is maintained by a community of contributors and releases focus on compatibility with modern TypeScript versions and evolving database drivers.

Limitations and considerations: TypeORM offers a rich feature set, but its complexity can be a trade-off for smaller projects. Some users evaluate alternative ORMs for highly specialized or performance-critical workloads, and ongoing maintenance status may influence long-term planning.