feat(asyncContainsOnce): add asyncContainsOnce function

Author: djcsdy

index.test.ts

@@ -1,6 +1,7 @@
 import type {ExecutionContext} from "ava";
 import test from "ava";
 import {
+    asyncContainsOnce,
     asyncDropOnce,
     asyncDropUntilOnce,
     asyncDropWhileOnce,
@@ -421,3 +422,8 @@ test("asyncIndexOnce", async t => {
     t.is(await asyncIndexOnce(asyncIterator([1, 2, 3, 4, 3, 2, 1]), 2), 3);
     t.is(await asyncIndexOnce(asyncIterator([1, 2, 3, 4, 3, 2, 1]), 7), null);
 });
+
+test("asyncContainsOnce", async t => {
+    t.true(await asyncContainsOnce(asyncIterator([1, 2, 3]), 1));
+    t.false(await asyncContainsOnce(asyncIterator([1, 2, 3]), 0));
+});

index.ts

@@ -701,3 +701,25 @@ export function asyncIndexOnceFn<T>(
 ): (iterator: AsyncIteratorLike<T>) => Promise<T | null> {
     return async iterator => asyncIndexOnce(iterator, index);
 }
+
+export async function asyncContainsOnce<T>(
+    iterator: AsyncIteratorLike<T>,
+    value: T | Promise<T>
+): Promise<boolean> {
+    const it = asyncIterator(iterator);
+    const [v, e] = await Promise.all([value, it.next()] as const);
+    let element = e;
+    while (element.done !== true) {
+        if (element.value === v) {
+            return true;
+        }
+        element = await it.next();
+    }
+    return false;
+}
+
+export function asyncContainsOnceFn<T>(
+    value: T | Promise<T>
+): (iterator: AsyncIteratorLike<T>) => Promise<boolean> {
+    return async iterator => asyncContainsOnce(iterator, value);
+}