feat(product): add product function

Author: djcsdy

index.test.ts

@@ -26,6 +26,7 @@ import {
     notEmpty,
     only,
     prefixMatch,
+    product,
     push,
     remove,
     removeFirst,
@@ -256,3 +257,9 @@ test("sum", async t => {
     t.is(await sum(asyncIterable([1, 2, 3])), 6);
     t.is(await sum(asyncIterable([])), 0);
 });
+
+test("product", async t => {
+    t.is(await product(asyncIterable([1, 2, 3])), 6);
+    t.is(await product(asyncIterable([1, 2, 3, 2])), 12);
+    t.is(await product(asyncIterable([])), 1);
+});

index.ts

@@ -830,3 +830,9 @@ export async function sum(iterable: AsyncIterableLike<number>): Promise<number>
 }
 
 export const asyncSum = sum;
+
+export async function product(iterable: AsyncIterableLike<number>): Promise<number> {
+    return fold(iterable, (product, element) => product * element, 1);
+}
+
+export const asyncProduct = product;