Libraries
The HTTP client people reach for out of habit — interceptors and automatic JSON handling that raw fetch still makes you write yourself.
Immutable, tree-shakable date functions that dodge the footguns of hand-rolled date math without dragging in Moment.js's weight.
The utility belt every JS codebase quietly leans on — unglamorous, but it saves you from reinventing array and object helpers.
Formerly Framer Motion, spun out on its own — the library that makes React transitions look hand-tuned instead of bolted on.
Handles server-state caching, retries, and refetching so well that a lot of apps end up not needing a global state library at all.
TypeScript-first schema validation that infers your types straight from the schema, so you stop writing the same shape twice.
A state store you can wire up in five lines, no providers or boilerplate — the anti-Redux for apps that never needed Redux.