[fabric-core] Add basic array-element utility types

packages/fabric/core/src/array/array-element.spec.ts

@@ -0,0 +1,12 @@
+import { describe, expectTypeOf, test } from "vitest";
+
+describe("ArrayElement utils", () => {
+  test("Given an array, it should return the element type of the array", () => {
+    type ArrayElement<T extends readonly unknown[]> =
+      T extends readonly (infer U)[] ? U : never;
+
+    type result = ArrayElement<["a", "b", "c"]>;
+
+    expectTypeOf<result>().toEqualTypeOf<"a" | "b" | "c">();
+  });
+});

packages/fabric/core/src/array/array-element.ts

@@ -0,0 +1,17 @@
+/**
+ * Get the element type of an array.
+ */
+export type ArrayElement<T extends readonly unknown[]> =
+  T extends readonly (infer U)[] ? U : never;
+
+/**
+ * Get the first element type of a tuple.
+ */
+export type TupleFirstElement<T extends readonly unknown[]> =
+  T extends readonly [infer U, ...unknown[]] ? U : never;
+
+/**
+ * Get the LAST element type of a tuple.
+ */
+export type TupleLastElement<T extends readonly unknown[]> =
+  T extends readonly [...unknown[], infer U] ? U : never;

packages/fabric/core/src/array/index.ts

@@ -0,0 +1 @@
+export * from "./array-element.js";

packages/fabric/core/src/index.ts

@@ -1,3 +1,4 @@
+export * from "./array/index.js";
 export * from "./domain/index.js";
 export * from "./error/index.js";
 export * from "./record/index.js";