typeorm

This skill is a development guidelines reference for TypeORM, the full-featured ORM for TypeScript and JavaScript that supports multiple databases. It solves the problem of writing correct, idiomatic data-access code by codifying entity definitions, relationships, repository usage, query building, and data-source configuration, with a stated focus on the Data Mapper pattern and enterprise application architecture. It is a documentation-only SKILL.md with abundant code examples and no executable scripts.

The guide opens with core principles (Active Record vs Data Mapper support, decorator-based entities, broad database support across MySQL, PostgreSQL, SQLite, SQL Server, Oracle, and more, and cross-runtime support) and required tsconfig settings (`experimentalDecorators`, `emitDecoratorMetadata`, strict mode). It then demonstrates entity definitions with primary-key options, column decorators (including JSON, enum, soft-delete, and version columns), and the three relationship types (one-to-one, one-to-many/many-to-one, many-to-many) with join configuration. Repository-pattern examples cover find variants, create/save/update/delete, soft delete, custom repository classes, and the query builder for joins, aggregates, and batch inserts. A data-source configuration section shows a Postgres `DataSource` set up from environment variables.

Target users are TypeScript and Node.js developers building database-backed applications who want a consistent, example-driven TypeORM reference. Use cases include modeling entities and relationships, writing repository and query-builder code, configuring migrations and data sources, and following enterprise-oriented conventions.