feat(asyncAppendOnce): add asyncAppendOnce function

Author: djcsdy

index.test.ts

@@ -4,6 +4,7 @@ import {
     asyncAllOnce,
     asyncAndOnce,
     asyncAnyOnce,
+    asyncAppendOnce,
     asyncAverageOnce,
     asyncConcatOnce,
     asyncContainsOnce,
@@ -553,3 +554,20 @@ test("asyncPrependOnce", async t => {
         [1, 2, 3]
     );
 });
+
+test("asyncAppendOnce", async t => {
+    t.deepEqual(
+        await asyncToArrayOnce(asyncAppendOnce(asyncIterator([4, 5, 6]))(asyncIterator([1, 2, 3]))),
+        [1, 2, 3, 4, 5, 6]
+    );
+    t.deepEqual(
+        await asyncToArrayOnce(
+            asyncAppendOnce(asyncIterator<number>([]))(asyncIterator([1, 2, 3]))
+        ),
+        [1, 2, 3]
+    );
+    t.deepEqual(
+        await asyncToArrayOnce(asyncAppendOnce(asyncIterator([4, 5, 6]))(asyncIterator([]))),
+        [4, 5, 6]
+    );
+});

index.ts

@@ -1035,3 +1035,9 @@ export function asyncPrependOnce<T>(
 ): (b: AsyncIteratorLike<T>) => AsyncIterator<T> {
     return b => asyncConcatOnce([a, b]);
 }
+
+export function asyncAppendOnce<T>(
+    b: AsyncIteratorLike<T>
+): (a: AsyncIteratorLike<T>) => AsyncIterator<T> {
+    return a => asyncConcatOnce([a, b]);
+}