feat(noneNull): add noneNull function

Author: djcsdy

index.test.ts

@@ -30,6 +30,7 @@ import {
     maximumBy,
     minimum,
     minimumBy,
+    noneNull,
     notEmpty,
     only,
     or,
@@ -352,3 +353,10 @@ test("concatMap", async t => {
         "6"
     ]);
 });
+
+test("noneNull", async t => {
+    t.deepEqual(await noneNull(asyncIterable([1, 2, 3])), [1, 2, 3]);
+    t.is(await noneNull(asyncIterable([1, null, 3])), null);
+    t.is(await noneNull(asyncIterable([undefined, 2, 3])), null);
+    t.deepEqual(await noneNull(asyncIterable([])), []);
+});

index.ts

@@ -921,3 +921,18 @@ export function concatMapFn<T, U>(
 }
 
 export const asyncConcatMapFn = concatMapFn;
+
+export async function noneNull<T>(
+    iterable: AsyncIterableLike<T | null | undefined>
+): Promise<T[] | null> {
+    const result: T[] = [];
+
+    for await (const element of await iterable) {
+        if (element == null) {
+            return null;
+        }
+        result.push(element);
+    }
+
+    return result;
+}