From 6fe367e1b951ce32500e10768d717c5c5bcd2ac3 Mon Sep 17 00:00:00 2001
From: Tyler <26290074+thegitduck@users.noreply.github.com>
Date: Sat, 21 Dec 2024 15:34:30 -0800
Subject: [PATCH] add mapSeries

---
 README.md                   | 18 +++++++++++++++
 src/index.ts                |  3 ++-
 src/map-series.ts           | 34 +++++++++++++++++++++++++++
 src/test/map-series.test.ts | 46 +++++++++++++++++++++++++++++++++++++
 src/test/props.test.ts      |  2 +-
 5 files changed, 101 insertions(+), 2 deletions(-)
 create mode 100644 src/map-series.ts
 create mode 100644 src/test/map-series.test.ts

diff --git a/README.md b/README.md
index a9b8cd1..ed4b157 100644
--- a/README.md
+++ b/README.md
@@ -22,3 +22,21 @@ const result = await duckhawk.props({
   three: fetch("https://pokeapi.co/api/v2/pokemon/3").then((res) => res.json()),
 });
 ```
+
+### mapSeries
+
+Bluebird equivalent: http://bluebirdjs.com/docs/api/promise.mapseries.html
+
+This awaits each promise in series and passes the result to the iterator. The result of the iterator is
+returned as an array.
+
+```ts
+import duckhawk from "duckhawk";
+
+const result = await duckhawk.mapSeries(
+  [Promise.resolve(1), Promise.resolve(2), Promise.resolve(3)],
+  (item) => item + 1
+);
+
+console.log(result); // [2, 3, 4]
+```
diff --git a/src/index.ts b/src/index.ts
index 6b1b217..a5be186 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,3 +1,4 @@
 import { props } from "./props.ts";
+import { mapSeries } from "./map-series.ts";
 
-export default { props };
+export default { props, mapSeries };
diff --git a/src/map-series.ts b/src/map-series.ts
new file mode 100644
index 0000000..fec2d7b
--- /dev/null
+++ b/src/map-series.ts
@@ -0,0 +1,34 @@
+// deno-lint-ignore-file no-explicit-any
+
+/**
+ * run Promises all in series
+ *
+ * @param arr list of promises
+ * @param iterator map callback for each promise result
+ * @returns result of iterator for each promise
+ *
+ * @example
+ * ```ts
+ * const result = await duckhawk.mapSeries([
+ *   Promise.resolve(1),
+ *   Promise.resolve(2),
+ *   Promise.resolve(3),
+ * ], (item) => item + 1);
+ *
+ * console.log(result); // [2, 3, 4]
+ * ```
+ */
+export const mapSeries = async <
+  PromiseGiven extends Promise<any>,
+  IteratorResult
+>(
+  arr: PromiseGiven[],
+  iterator: (item: Awaited<PromiseGiven>, index: number) => IteratorResult
+): Promise<IteratorResult[]> => {
+  const results: IteratorResult[] = [];
+  for (let i = 0; i < arr.length; i++) {
+    const result = await iterator(await arr[i], i);
+    results.push(result);
+  }
+  return results;
+};
diff --git a/src/test/map-series.test.ts b/src/test/map-series.test.ts
new file mode 100644
index 0000000..7d4ab78
--- /dev/null
+++ b/src/test/map-series.test.ts
@@ -0,0 +1,46 @@
+import { mapSeries } from "../map-series.ts";
+import { expect } from "@std/expect";
+
+Deno.test("mapSeries simple", async () => {
+  const result = await mapSeries(
+    [Promise.resolve(1), Promise.resolve(2), Promise.resolve(3)],
+    (item) => item + 1
+  );
+  expect(result).toEqual([2, 3, 4]);
+});
+
+Deno.test("mapSeries with async", async () => {
+  const result = await mapSeries(
+    [Promise.resolve(1), Promise.resolve(2), Promise.resolve(3)],
+    async (item) => item + (await Promise.resolve(1))
+  );
+  expect(result).toEqual([2, 3, 4]);
+});
+
+Deno.test("mapSeries with mixed types", async () => {
+  const result = await mapSeries(
+    [
+      Promise.resolve(1),
+      Promise.resolve("hi"),
+      Promise.resolve({ foo: "bar" }),
+    ],
+    (item) => (typeof item === "object" ? item : item + "!")
+  );
+  expect(result).toEqual(["1!", "hi!", { foo: "bar" }]);
+});
+
+Deno.test("mapSeries executes in order", async () => {
+  const order: number[] = [];
+  const result = await mapSeries(
+    [Promise.resolve(1), Promise.resolve(2), Promise.resolve(3)],
+    (item, ind) => {
+      order.push(item);
+      expect(order).toEqual(
+        Array.from({ length: ind + 1 }).map((_, i) => i + 1)
+      );
+      return item;
+    }
+  );
+
+  expect(result).toEqual([1, 2, 3]);
+});
diff --git a/src/test/props.test.ts b/src/test/props.test.ts
index f383586..60af4ff 100644
--- a/src/test/props.test.ts
+++ b/src/test/props.test.ts
@@ -2,7 +2,7 @@ import { props } from "../props.ts";
 import { expect } from "@std/expect";
 import { delayedReject } from "./utils.ts";
 
-Deno.test("props", async () => {
+Deno.test("props simple", async () => {
   const result = await props({
     a: Promise.resolve(1),
     b: Promise.resolve(2),
-- 
2.51.2