Dependency injection

Dependency Injection (DI) is a design pattern for organizing and sharing code by supplying dependencies to a class instead of creating them internally, thereby enhancing reusability and manageability as applications grow. This approach addresses key challenges: it improves code maintainability through clear separation of concerns, facilitating easier refactoring and reduced duplication; it aids scalability by enabling the reuse of modular functionality across different application parts; and it supports better testing by allowing unit tests to substitute real implementations with test doubles. A dependency is any object, value, function, or service a class requires but does not create itself. You interact with the DI system by providing values to make them available and injecting them as dependencies. Injected values can be JavaScript objects, functions, or class instances, including configuration values, factories, and services. Scope: Angular. Reviewed October 4, 2026.