lib0/src/ts.js

isomorphic utility functions

/**
 * @template T
 * @template Then
 * @template Else
 * @typedef {0 extends (1 & T) ? Then : Else} TypeIsAny
 */

/**
 * Resolve a type with all sub-properties. Useful for returning prettified results.
 * @template T
 * @template {number} [Depth=10]
 * @template {any[]} [Cache=[]]
 * @typedef {Cache['length'] extends Depth ? T : T extends object ? { [K in keyof T]: Prettify<T[K], Depth, [any, ...Cache]> } & {} : T} Prettify
 */

/**
 * @template {true} C
 * @typedef {C} Assert
 */

/**
 * @template A
 * @template B
 * @typedef {(<T>() => T extends A ? 1 : 2) extends (<T>() => T extends B ? 1 : 2) ? true : false} Equal
 */

/**
 * @template {B} A
 * @template B
 * @typedef {A} AssertExtends
 */

/**
 * In typescript `keyof {[k:string]:any}` is `string|number` instead of `string`. This KeyOf type returns the expected
 * result. Use this for pretty-printing onyly.
 *
 * @template {{[K:string|number|symbol]:any}} Obj
 * @typedef {{ [K in keyof Obj]: K }[keyof Obj]} KeyOf
 */

/**
 * For each key-value pair in Renames, rename O[Key] to O[Renames[Key]]
 * @template {{[K in string|number]:any}} OBJ
 * @template {{[K:string|number]:string|number}} Renames - pairs of renames
 * @typedef {{[K in keyof OBJ as K extends keyof Renames ? Renames[K] : K extends Renames[keyof Renames] ? never : K]: OBJ[K]}} PropsRename
 */

/**
 * Convert a union type to an intersection type.
 *
 * @example
 * // { a: string } & { b: number }
 * type R = UnionToIntersection<{ a: string } | { b: number }>
 *
 * @template U
 * @typedef {(U extends any ? (k: U) => void : never) extends ((k: infer I) => void) ? I : never} UnionToIntersection
 */

/**
 * Merge two objects, keeping only keys present in both with intersected value types.
 * e.g. IntersectObjects<{a:string,b:string|number},{b:string,c:number}> = {b:string}
 *
 * @template A
 * @template B
 * @typedef {{[K in keyof A & keyof B]: Extract<B[K], A[K]>} & {}} PropsPickShared
 */