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feat(transducers): add toggle() xform
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,44 @@ | ||
| import { Reducer, Transducer } from "../api"; | ||
| import { iterator1 } from "../iterator"; | ||
|
|
||
| /** | ||
| * Stateful transducer which accepts any input and flips between given | ||
| * `on` / `off` values for every value received. The `initial` state can | ||
| * be optionally provided (default: false) and must be given if used as | ||
| * an iterator. | ||
| * | ||
| * ``` | ||
| * [...toggle(1, 0, false, [1, 2, 3, 4])] | ||
| * // [ 1, 0, 1, 0 ] | ||
| * | ||
| * [...tx.toggle("on", "off", true, [1, 2, 3, 4])] | ||
| * // [ 'off', 'on', 'off', 'on' ] | ||
| * ``` | ||
| * @param on result for "on" state | ||
| * @param off result for "off" state | ||
| * @param initial initial state | ||
| */ | ||
| export function toggle<T>(on: T, off: T, initial?: boolean): Transducer<any, T>; | ||
| export function toggle<T>( | ||
| on: T, | ||
| off: T, | ||
| initial: boolean, | ||
| src: Iterable<any> | ||
| ): IterableIterator<boolean>; | ||
| export function toggle<T>( | ||
| on: T, | ||
| off: T, | ||
| initial = false, | ||
| src?: Iterable<any> | ||
| ): any { | ||
| return src | ||
| ? iterator1(toggle(on, off, initial), src) | ||
| : ([init, complete, reduce]: Reducer<any, T>) => { | ||
| let state = initial; | ||
| return [ | ||
| init, | ||
| complete, | ||
| (acc) => reduce(acc, (state = !state) ? on : off) | ||
| ]; | ||
| }; | ||
| } |