feat(asyncConcatMapOnce): add asyncConcatMapOnce function

Author: djcsdy

index.test.ts

@@ -6,6 +6,7 @@ import {
     asyncAnyOnce,
     asyncAppendOnce,
     asyncAverageOnce,
+    asyncConcatMapOnce,
     asyncConcatOnce,
     asyncContainsOnce,
     asyncDropOnce,
@@ -571,3 +572,12 @@ test("asyncAppendOnce", async t => {
         [4, 5, 6]
     );
 });
+
+test("asyncConcatMapOnce", async t => {
+    t.deepEqual(
+        await asyncToArrayOnce(
+            asyncConcatMapOnce(asyncIterator(["1,2,3", "4,5,6"]), s => s.split(","))
+        ),
+        ["1", "2", "3", "4", "5", "6"]
+    );
+});

index.ts

@@ -1041,3 +1041,16 @@ export function asyncAppendOnce<T>(
 ): (a: AsyncIteratorLike<T>) => AsyncIterator<T> {
     return a => asyncConcatOnce([a, b]);
 }
+
+export function asyncConcatMapOnce<T, U>(
+    iterator: AsyncIteratorLike<T>,
+    f: (element: T, index: number) => AsyncIteratorLike<U>
+): AsyncIterator<U> {
+    return asyncConcatOnce(asyncMapOnce(iterator, f));
+}
+
+export function asyncConcatMapOnceFn<T, U>(
+    f: (element: T, index: number) => AsyncIteratorLike<U>
+): (iterator: AsyncIteratorLike<T>) => AsyncIterator<U> {
+    return iterator => asyncConcatMapOnce(iterator, f);
+}