More functions (#4)

- Add compact
- Fix
- Fix
- Fix
- Fix

src/compact.test.ts

@@ -0,0 +1,20 @@
+import { it, expect } from "vitest";
+import { compact } from "./compact.js";
+
+for (const [xs, y] of [
+  [[0], []],
+  [[""], []],
+  [[undefined], []],
+  [[null], []],
+  [[false], []],
+  [
+    [-1, 0, 1],
+    [-1, 1],
+  ],
+] satisfies [unknown[], unknown[]][]) {
+  it(`finds the last element in an array ${JSON.stringify(xs)}`, () => {
+    const zs: unknown[] = xs;
+
+    expect(compact(zs)).toEqual(y);
+  });
+}

src/compact.ts

@@ -0,0 +1,4 @@
+export const compact = <T>(
+  xs: T[],
+): Exclude<T, 0 | "" | false | null | undefined>[] =>
+  xs.filter(Boolean) as Exclude<T, 0 | "" | false | null | undefined>[];

src/main.ts

@@ -1,3 +1,4 @@
+export * from "./compact.js";
 export * from "./identity.js";
 export * from "./last.js";
 export * from "./once.js";