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reverse.ts
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reverse.ts
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import { isAsyncIterable, isIterable } from "../_internal/utils";
import isArray from "../isArray";
import isString from "../isString";
import toArray from "../toArray";
import type ReturnIterableIteratorType from "../types/ReturnIterableIteratorType";
import concurrent, { isConcurrent } from "./concurrent";
function* sync<T>(iterable: Iterable<T>) {
const arr =
isArray(iterable) || isString(iterable) ? iterable : toArray(iterable);
for (let i = arr.length - 1; i >= 0; i--) {
yield arr[i];
}
}
async function* asyncSequential<T>(iterable: AsyncIterable<T>) {
const arr = await toArray(iterable);
for (let i = arr.length - 1; i >= 0; i--) {
yield arr[i];
}
}
function async<T>(iterable: AsyncIterable<T>): AsyncIterableIterator<T> {
let iterator: AsyncIterator<T>;
return {
[Symbol.asyncIterator]() {
return this;
},
async next(_concurrent: any) {
if (iterator === undefined) {
iterator = isConcurrent(_concurrent)
? asyncSequential(concurrent(_concurrent.length, iterable))
: asyncSequential(iterable);
}
return iterator.next(_concurrent);
},
};
}
/**
* Returns Iterable/AsyncIterable of the given elements in reverse order.
* Note:Evaluates all Iterable, except for array, and returns a lazy-reversed iterator.
*
* @example
* ```ts
* const iter1 = reverse([1, 2, 3]);
* iter1.next(); // {value: 3, done: false}
* iter1.next(); // {value: 2, done: false}
* iter1.next(); // {value: 1, done: false}
* iter1.next(); // {value: undefined, done: true}
*
* const iter2 = reverse("abc");
* iter2.next(); // {value: "c", done: false}
* iter2.next(); // {value: "b", done: false}
* iter2.next(); // {value: "a", done: false}
* iter2.next(); // {value: undefined, done: true}
*
* // with pipe
* pipe(
* [1, 2, 3, 4, 5],
* reverse,
* toArray,
* ); // [5, 4, 3, 2, 1]
*
* pipe(
* "abcde",
* reverse,
* toArray,
* ); // "edcba"
* ```
*
* see {@link https://fxts.dev/docs/pipe | pipe} {@link https://fxts.dev/docs/toArray | toArray}
*/
function reverse<T extends Iterable<unknown> | AsyncIterable<unknown>>(
iterable: T,
): ReturnIterableIteratorType<T>;
function reverse<T extends Iterable<unknown> | AsyncIterable<unknown>>(
iterable: T,
) {
if (isIterable(iterable)) {
return sync(iterable);
}
if (isAsyncIterable(iterable)) {
return async(iterable);
}
throw new TypeError("'iterable' must be type of Iterable or AsyncIterable");
}
export default reverse;