feat(asyncMapKeyLastByOnce): add asyncMapKeyLastByOnce function

Author: djcsdy

index.test.ts

@@ -32,6 +32,7 @@ import {
     asyncLastOnce,
     asyncMapKeyByOnce,
     asyncMapKeyFirstByOnce,
+    asyncMapKeyLastByOnce,
     asyncMapOnce,
     asyncMaximumByOnce,
     asyncMaximumOnce,
@@ -693,3 +694,14 @@ test("asyncMapKeyFirstByOnce", async t => {
     t.is(map.get("odd"), "1");
     t.deepEqual(Array.from(map.keys()), ["odd", "even"]);
 });
+
+test("asyncMapKeyLastByOnce", async t => {
+    const map = await asyncMapKeyLastByOnce(asyncIterator([1, 3, 4, 2, 5, 6]), e => [
+        e % 2 === 0 ? "even" : "odd",
+        String(e)
+    ]);
+    t.deepEqual(Array.from(map.entries()), [
+        ["odd", "5"],
+        ["even", "6"]
+    ]);
+});

index.ts

@@ -1332,3 +1332,32 @@ export function asyncMapKeyFirstByOnceFn<TKey, TElement, TNewElement>(
 ): (iterator: AsyncIteratorLike<TElement>) => Promise<Map<TKey, TNewElement>> {
     return async iterator => asyncMapKeyFirstByOnce(iterator, f);
 }
+
+export async function asyncMapKeyLastByOnce<TKey, TElement, TNewElement>(
+    iterator: AsyncIteratorLike<TElement>,
+    f: (
+        element: TElement,
+        index: number
+    ) => readonly [TKey, TNewElement] | Promise<readonly [TKey, TNewElement]>
+): Promise<Map<TKey, TNewElement>> {
+    const it = asyncIterator(iterator);
+    const map = new Map<TKey, TNewElement>();
+    for (
+        let i = 0, element = await it.next();
+        element.done !== true;
+        ++i, element = await it.next()
+    ) {
+        const [key, value] = await f(element.value, i);
+        map.set(key, value);
+    }
+    return map;
+}
+
+export function asyncMapKeyLastByOnceFn<TKey, TElement, TNewElement>(
+    f: (
+        element: TElement,
+        index: number
+    ) => readonly [TKey, TNewElement] | Promise<readonly [TKey, TNewElement]>
+): (iterator: AsyncIteratorLike<TElement>) => Promise<Map<TKey, TNewElement>> {
+    return async iterator => asyncMapKeyLastByOnce(iterator, f);
+}