[dayongkr]

Overview

Adds seven compile-time type utilities to es-toolkit/types, and groups the reference sidebar by category.

Type	What it does
IsEqual<A, B>	true when two types are exactly the same
Primitive	Union of every primitive value in JavaScript
JsonValue	Any value JSON.parse can produce
UnknownRecord	An object with unknown keys and values, for use instead of {}
EmptyObject	An object with no properties, pairs with isEmptyObject
SetOptional<T, K>	Partial scoped to specific keys
SetRequired<T, K>	Required scoped to specific keys

Reference pages are added in all four languages. Merge and ObjectKeys were exported and documented but missing from the intro table, so they are listed there as well.

Notes on a few choices

IsEqual uses the conditional-type variance trick, which is hard to write by hand and tells any apart from every other type. The same trick already exists in compat/_internal/Equals.d.ts; that copy is left untouched to keep this change out of compat.

JsonValue follows RFC 8259 and is recursive. It ships as a single self-contained type rather than a JsonObject / JsonArray / JsonPrimitive family, since each of those is a one-liner at the call site (JsonValue[], Record<string, JsonValue>).

SetOptional and SetRequired both survive a union, so each member can still be told apart afterwards. Their definitions differ, and the specs record why:

export type SetOptional<T, K extends keyof T> = T extends unknown ? Simplify<Omit<T, K> & Partial<Pick<T, K>>> : never;
export type SetRequired<T, K extends keyof T> = Simplify<T & Required<Pick<T, K>>>;

Omit collapses a union to its shared keys, so SetOptional needs the conditional type. An intersection leaves the union alone, so SetRequired does not. Both were checked against type-fest and produce identical results across the cases that matter (readonly and optional modifiers, multiple keys, unions, index signatures).

Sidebar

The types were listed flat. They are now split into objects (14) / values (5) / predicate (1) through the categories field in flavors.mts, the same mechanism es-toolkit/compat already uses. The split is by what a type takes, so the key conversion types sit with the other object types.

labels.categories is shared across flavors, so es-toolkit/types could not label its own predicate group without changing the runtime one. buildFlavorSidebar now looks up <flavor>:<category> before falling back to the shared key. Existing flavors are untouched.

Reference pages move into matching folders, so their URLs gain a segment (/types/reference/ValueOf -> /types/reference/objects/ValueOf). Links in the intro, inside the moved pages, and coming in from the runtime function docs are all updated.

Verification

• vitest run src/types --typecheck passes, 66 tests
• Every example in the new docs compiles under tsc --strict, including the failing cases marked in comments
• Sidebar built through buildFlavorSidebar for all four locales
• All 2,159 relative links across docs resolve

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Project	Deployment	Actions	Updated (UTC)
es-toolkit	Ready	Preview	Aug 26, 2026 11:43am