LibJS: Add %TypedArray%.prototype.reverse

This fixes 13 test262 cases.

Userland/Libraries/LibJS/Runtime/TypedArrayPrototype.cpp

@@ -39,6 +39,7 @@ void TypedArrayPrototype::initialize(GlobalObject& object)
     define_native_function(vm.names.values, values, 0, attr);
     define_native_function(vm.names.entries, entries, 0, attr);
     define_native_function(vm.names.set, set, 1, attr);
+    define_native_function(vm.names.reverse, reverse, 0, attr);
 
     define_native_accessor(*vm.well_known_symbol_to_string_tag(), to_string_tag_getter, nullptr, Attribute::Configurable);
 
@@ -486,4 +487,46 @@ JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::set)
     return js_undefined();
 }
 
+// 23.2.3.22 %TypedArray%.prototype.reverse ( ), https://tc39.es/ecma262/#sec-%typedarray%.prototype.reverse
+JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::reverse)
+{
+    // 1. Let O be the this value.
+    // 2. Perform ? ValidateTypedArray(O).
+    auto* typed_array = typed_array_from(vm, global_object);
+    if (!typed_array)
+        return {};
+
+    // 3. Let len be O.[[ArrayLength]].
+    auto length = typed_array->array_length();
+
+    // 4. Let middle be floor(len / 2).
+    auto middle = length / 2;
+
+    // 5. Let lower be 0.
+    // 6. Repeat, while lower ≠ middle,
+    for (size_t lower = 0; lower != middle; ++lower) {
+        // a. Let upper be len - lower - 1.
+        auto upper = length - lower - 1;
+
+        // b. Let upperP be ! ToString(𝔽(upper)).
+        // d. Let lowerValue be ! Get(O, lowerP).
+        auto lower_value = typed_array->get(lower);
+
+        // c. Let lowerP be ! ToString(𝔽(lower)).
+        // e. Let upperValue be ! Get(O, upperP).
+        auto upper_value = typed_array->get(upper);
+
+        // f. Perform ! Set(O, lowerP, upperValue, true).
+        typed_array->set(lower, upper_value, true);
+
+        // g. Perform ! Set(O, upperP, lowerValue, true).
+        typed_array->set(upper, lower_value, true);
+
+        // h. Set lower to lower + 1.
+    }
+
+    // 7. Return O.
+    return typed_array;
+}
+
 }

Userland/Libraries/LibJS/Runtime/TypedArrayPrototype.h

@@ -36,6 +36,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(values);
     JS_DECLARE_NATIVE_FUNCTION(entries);
     JS_DECLARE_NATIVE_FUNCTION(set);
+    JS_DECLARE_NATIVE_FUNCTION(reverse);
 };
 
 }

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

@@ -0,0 +1,67 @@
+const TYPED_ARRAYS = [
+    Uint8Array,
+    Uint8ClampedArray,
+    Uint16Array,
+    Uint32Array,
+    Int8Array,
+    Int16Array,
+    Int32Array,
+    Float32Array,
+    Float64Array,
+];
+
+const BIGINT_TYPED_ARRAYS = [BigUint64Array, BigInt64Array];
+
+test("length is 0", () => {
+    TYPED_ARRAYS.forEach(T => {
+        expect(T.prototype.reverse).toHaveLength(0);
+    });
+
+    BIGINT_TYPED_ARRAYS.forEach(T => {
+        expect(T.prototype.reverse).toHaveLength(0);
+    });
+});
+
+describe("basic functionality", () => {
+    test("Odd length array", () => {
+        TYPED_ARRAYS.forEach(T => {
+            const array = new T([1, 2, 3]);
+            expect(array.reverse()).toEqual([3, 2, 1]);
+            expect(array).toEqual([3, 2, 1]);
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            const array = new T([1n, 2n, 3n]);
+            expect(array.reverse()).toEqual([3n, 2n, 1n]);
+            expect(array).toEqual([3n, 2n, 1n]);
+        });
+    });
+
+    test("Even length array", () => {
+        TYPED_ARRAYS.forEach(T => {
+            const array = new T([1, 2]);
+            expect(array.reverse()).toEqual([2, 1]);
+            expect(array).toEqual([2, 1]);
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            const array = new T([1n, 2n]);
+            expect(array.reverse()).toEqual([2n, 1n]);
+            expect(array).toEqual([2n, 1n]);
+        });
+    });
+
+    test("Empty array", () => {
+        TYPED_ARRAYS.forEach(T => {
+            const array = new T([]);
+            expect(array.reverse()).toEqual([]);
+            expect(array).toEqual([]);
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            const array = new T([]);
+            expect(array.reverse()).toEqual([]);
+            expect(array).toEqual([]);
+        });
+    });
+});