Lifetimes

TinyDI supports exactly two lifetimes, via the ServiceLifetime enum. There is no third option, and no automatic detection — you state the lifetime you want.

enum ServiceLifetime {
  Singleton,
  Transient,
}

Singleton

The default. The first time a token is resolved, its factory runs once; every later resolve() call for the same token returns that same instance.

container.registerFactory(ClockToken, () => new SystemClock()); // Singleton by default
 
container.resolve(ClockToken) === container.resolve(ClockToken); // true

registerInstance is always Singleton — you are handing the container an instance that already exists, so there is nothing else it could be.

Transient

A new instance is created on every resolve() call.

container.registerFactory(RequestIdToken, () => crypto.randomUUID(), ServiceLifetime.Transient);
 
container.resolve(RequestIdToken) === container.resolve(RequestIdToken); // false

Choosing between them

• Default to Singleton for stateless services and shared resources (repositories, HTTP clients, loggers).
• Reach for Transient only when each resolution genuinely needs a fresh instance — a per-operation identifier, a builder object that accumulates state during one use.