switch-functional
Version:
Functional switch statement
89 lines (88 loc) • 3.47 kB
TypeScript
export type { Condition, Options, Switch } from './types.js';
/**
* Functional switch statement. This must be chained with
* `.case()` statements and end with `.default()`.
*
* @example <caption>Basic usage</caption>
* ```js
* import switchFunctional from 'switch-functional'
*
* const getUserType = (user) =>
* switchFunctional(user.type)
* .case('dev', 'developer')
* .case(['admin', 'owner'], 'administrator')
* .default('unknown')
* ```
*
* This is equivalent to:
*
* ```js
* const getUserType = (user) => {
* switch (user.type) {
* case 'dev': {
* return 'developer'
* }
*
* case 'admin':
*
* case 'owner': {
* return 'administrator'
* }
*
* default: {
* return 'unknown'
* }
* }
* }
* ```
*
* @example <caption>Testing input</caption>
* ```js
* const getUserType = (user) =>
* switchFunctional(user)
* .case(isDeveloper, 'developer')
* .case([isAdmin, isOwner], 'admin')
* .default('unknown')
* ```
*
* This is equivalent to:
*
* ```js
* const getUserType = (user) => {
* if (isDeveloper(user)) {
* return 'developer'
* }
*
* if (isAdmin(user) || isOwner(user)) {
* return 'admin'
* }
*
* return 'unknown'
* }
* ```
*
* @example <caption>Testing properties</caption>
* ```js
* const getUserType = (user) =>
* switchFunctional(user)
* // Checks `user.hasDevProjects === true`
* .case({ hasDevProjects: true }, 'developer')
* // Checks for deep properties
* .case({ devProjectsCount: 0, permissions: { admin: true } }, 'admin')
* .default('unknown')
* ```
*
* @example <caption>Returning dynamic values</caption>
* ```js
* const getUserType = (user) =>
* switchFunctional(user)
* .case(isDeveloper, (user) => user.developerType)
* .case(isAdmin, (user) => user.adminType)
* .default((user) => user.genericType)
* ```
*/
declare const switchFunctional: <OriginalInput extends import("./types.js").Input, CustomCondition = never, CustomReturnValues extends readonly unknown[] = never, StrictReturnValue extends import("./types.js").ReturnValue<OriginalInput> = never>(input: OriginalInput, options?: import("./types.js").Options<CustomCondition, CustomReturnValues, OriginalInput, StrictReturnValue>) => {
case: <NewReturnValue extends import("./types.js").ReturnValue<OriginalInput> = never>(conditions: import("./types.js").AnyConditions<CustomCondition, OriginalInput>, ...caseReturnValues: import("./types.js").AnyReturnValues<CustomReturnValues, OriginalInput, NewReturnValue>) => import("./types.js").Switch<(NewReturnValue[] extends never[] ? StrictReturnValue : NewReturnValue) extends infer T ? T extends (NewReturnValue[] extends never[] ? StrictReturnValue : NewReturnValue) ? T extends (...args: readonly never[]) => unknown ? ReturnType<T> : T : never : never, CustomCondition, CustomReturnValues, OriginalInput, StrictReturnValue>;
default: <NewReturnValue extends import("./types.js").ReturnValue<OriginalInput> = never>(...defaultReturnValues: import("./types.js").AnyReturnValues<CustomReturnValues, OriginalInput, NewReturnValue>) => (NewReturnValue[] extends never[] ? StrictReturnValue : NewReturnValue) extends infer T ? T extends (NewReturnValue[] extends never[] ? StrictReturnValue : NewReturnValue) ? T extends (...args: readonly never[]) => unknown ? ReturnType<T> : T : never : never;
};
export default switchFunctional;