♻️ Update

Author: UltiRequiem

src/language/filter.test.ts

@@ -1,7 +1,19 @@
 import { filter } from "./filter.ts";
 import { assertEquals } from "../../deps.ts";
 
-Deno.test("filter", () => {
-  const data = filter([1, 2, 3, 4, 5], (item) => item % 2 === 0);
-  assertEquals(data, [2, 4]);
+const data = [1, 2, 3, 4, 5];
+
+const cb = (item: number) => item % 2 === 0;
+
+Deno.test("[filter]", () => {
+  const result = filter(data, cb);
+
+  assertEquals(result, [2, 4]);
+});
+
+Deno.test("[filter vs Array.filter]", () => {
+  const expected = data.filter(cb);
+  const result = filter(data, cb);
+
+  assertEquals(result, expected);
 });

src/language/filter.ts

@@ -2,7 +2,7 @@ export type FilterCallback<T> = (
   item: T,
   index: number,
   array: readonly T[],
-) => boolean;
+) => unknown;
 
 export function filter<T>(array: readonly T[], test: FilterCallback<T>) {
   const result: T[] = [];