fw-01 — Broader Ideas

Where the guards reappear

Iterating a collection that callbacks can mutate is a bug class, not an edge case. Having hit it once here, you will recognise it in unfamiliar code.

Narrow API over powerful API

applyMiddleware is an enhancer, packaged so the common case is easy. Middleware has a trivially composable signature; enhancers are strictly more powerful and easy to make mutually incompatible.

That pattern — constrained interface for the 95% case, escape hatch for the rest, the former implemented in terms of the latter — is one you will design yourself. Compare useState on useReducer, or CSS custom properties versus Houdini.

The state-at-a-moment property

Explicit-update models make "the whole state at time T" a first-class value. Time travel, serialisation, undo, crash-report state dumps, and deterministic replay all follow from it — and none of them follow from update efficiency.

When you choose a state architecture, ask whether you will ever need to reproduce a user's exact state. If yes, that requirement outranks per-update cost, and this is the trade fw-03 makes in the other direction.

Next

fw-02 is the consumer that makes Redux's notify-everyone default expensive; fw-03 is the opposite architecture; §47 is where you write the comparison rather than accept one.