feat(mapKeyLastByOnce): add mapKeyLastByOnce function

Author: djcsdy

index.test.ts

@@ -31,6 +31,7 @@ import {
     lastOnce,
     mapKeyByOnce,
     mapKeyFirstByOnce,
+    mapKeyLastByOnce,
     mapOnce,
     maximumByOnce,
     maximumOnce,
@@ -500,3 +501,14 @@ test("mapKeyFirstByOnce", t => {
     t.is(map.get("odd"), "1");
     t.deepEqual(Array.from(map.keys()), ["odd", "even"]);
 });
+
+test("mapKeyLastByOnce", t => {
+    const map = mapKeyLastByOnce(iterator([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

@@ -1114,3 +1114,22 @@ export function mapKeyFirstByOnceFn<TKey, TElement, TNewElement>(
 ): (iterator: IteratorLike<TElement>) => Map<TKey, TNewElement> {
     return iterator => mapKeyFirstByOnce(iterator, f);
 }
+
+export function mapKeyLastByOnce<TKey, TElement, TNewElement>(
+    iterator: IteratorLike<TElement>,
+    f: (element: TElement, index: number) => readonly [TKey, TNewElement]
+): Map<TKey, TNewElement> {
+    const it = toIterator(iterator);
+    const map = new Map<TKey, TNewElement>();
+    for (let i = 0, element = it.next(); element.done !== true; ++i, element = it.next()) {
+        const [key, value] = f(element.value, i);
+        map.set(key, value);
+    }
+    return map;
+}
+
+export function mapKeyLastByOnceFn<TKey, TElement, TNewElement>(
+    f: (element: TElement, index: number) => readonly [TKey, TNewElement]
+): (iterator: IteratorLike<TElement>) => Map<TKey, TNewElement> {
+    return iterator => mapKeyLastByOnce(iterator, f);
+}