ReadonlyView is one way to model ownership. It is not a replacement for every form of readonly or immutable state. Choose the tool that matches the lifecycle you need.
Choose TypeScript readonly when you need compile-time guidance for a typed API and runtime enforcement is not required. It does not change JavaScript behavior: a consumer can still mutate a value at runtime if it has a mutable reference or casts around the type.
Choose Object.freeze when a shallow runtime boundary is enough and preventing top-level writes on that particular object is acceptable. Its nested objects remain mutable, and freezing the owner’s object means the owner cannot continue changing top-level properties.
Choose deep freeze when a value must become deeply immutable and neither owner nor consumer should update it. It eagerly traverses the reachable graph and changes the source objects’ mutability, so it does not fit a live owner-controlled surface.
Choose cloning or snapshots when consumers need a historical, isolated point in time. A snapshot intentionally becomes stale after its creation; make a new one when the source changes.
Choose an Immer-style immutable-update workflow when the primary job is to produce successor state from convenient draft mutations. The draft is a controlled working surface for an update; the result is a new state value, often with structural sharing. This is a state-production workflow, not a way to publish one owner-controlled live graph to consumers.
Choose ReadonlyView when an owner continues to mutate a live graph, consumers must see those changes through an existing reference, and consumers must not mutate through that public access path. It creates a lazy runtime membrane without freezing, copying, or managing state.
| Capability | TypeScript readonly |
Object.freeze |
Deep freeze | Snapshot / Immer | ReadonlyView |
|---|---|---|---|---|---|
| Compile-time protection | Yes, where typed | No | No | Optional types | Yes |
| Runtime depth | None | Shallow | Deep | Snapshot/draft-specific | Deep |
| Owner retains mutation | Yes | Top-level no; nested yes | No | Yes, on original | Yes |
| Live owner updates | Yes | Nested updates remain live | N/A: owner is frozen | No: new snapshot/state | Yes |
| Traversal/copying | None | None | Eager traversal | Produces/copies state | Lazy, on access |
| New-state production | No | No | No | Yes | No |
These approaches solve different ownership and lifecycle problems. Immer helps create new state; snapshots preserve a past state; freezing constrains the source itself; TypeScript guides typed consumers. ReadonlyView exposes an existing owner-controlled graph without granting mutation through the view.