Dependencies stay explicit
Read the contract at the function boundary. TypeScript verifies every connection.
Dependency graphs, just typed functions.
v3 · TypeScript-first DI
Explicit dependencies. Replaceable boundaries. No decorators, reflection, or container ceremony.
npm install @favy/di import { Module, type Live } from '@favy/di';
const Clock = Module()('Clock', () => ({
now: () => new Date(),
}));
type ClockLive = Live<typeof Clock>;
const Greeting = Module<ClockLive>()(
'Greeting',
({ Clock }) => ({
message: () => 'Hello at ' + Clock.now().toISOString(),
}),
);
Greeting({ Clock }).message(); Clock is resolved when Greeting uses it. Types
verify the connection before the graph runs.
- 0 decorators
- Typed end to end
- Lazy by default
- Replaceable boundaries
One mental model
The graph is the configuration.
Each edge is an ordinary TypeScript contract. Follow it in the code, replace it in a test, or preconfigure it for the next caller.
- 01
Define
A module is a named function with a typed input and output.
- 02
Compose
ClockLive names Clock's output for reuse as a typed dependency.
- 03
Run
Supply implementations at the boundary and call the resulting graph.
Small API, deliberate control
Only the machinery your graph needs.
Start with typed functions. Add lifetime and transformation rules at the boundary where they matter.
Cache on your terms
Choose run, module, or no caching without changing the consumer.
Initialize only when used
Dependencies resolve lazily by default, including deep inside the graph.
Preconfigure a boundary
Provide part of a graph once, then expose only what the caller should supply.
Replace values, not machinery
Pass a small fake at the same typed boundary—there is no container to reset.
Shape the edges
Transform input and output while preserving inference through the graph.
Documentation paths
Go straight to the work at hand.
The core stays small. Pick a path when you need the next layer of control.
Extend
Use transformations and exact signatures when the graph gets advanced.
Build the first edge