LibJS: Expose TypedArray.prototype.byteOffset

Userland/Libraries/LibJS/Tests/builtins/TypedArray/TypedArray.prototype.byteOffset.js

@@ -0,0 +1,28 @@
+// Update when more typed arrays get added
+const TYPED_ARRAYS = [
+    Uint8Array,
+    Uint16Array,
+    Uint32Array,
+    Int8Array,
+    Int16Array,
+    Int32Array,
+    Float32Array,
+    Float64Array,
+];
+
+test("basic functionality", () => {
+    TYPED_ARRAYS.forEach(T => {
+        const typedArray = new T([1, 2, 3]);
+        expect(Object.hasOwn(typedArray, "byteOffset")).toBeFalse();
+        expect(typedArray.byteOffset).toBe(0);
+        expect(typedArray.length).toBe(3);
+
+        const buffer = typedArray.buffer;
+
+        const arrayFromOffset = new T(buffer, T.BYTES_PER_ELEMENT);
+        expect(arrayFromOffset.byteOffset).toBe(T.BYTES_PER_ELEMENT);
+        expect(arrayFromOffset.length).toBe(2);
+        expect(arrayFromOffset[0]).toBe(2);
+        expect(arrayFromOffset[1]).toBe(3);
+    });
+});