LibJS: Add %TypedArray%.prototype.map

Author: https://github.com/Lubrsi
Commit: https://github.com/SerenityOS/serenity/commit/1da06f9dfd8
Pull-request: https://github.com/SerenityOS/serenity/pull/8573

Userland/Libraries/LibJS/Runtime/TypedArrayPrototype.cpp

@@ -48,6 +48,7 @@ void TypedArrayPrototype::initialize(GlobalObject& object)
     define_native_function(vm.names.reverse, reverse, 0, attr);
     define_native_function(vm.names.copyWithin, copy_within, 2, attr);
     define_native_function(vm.names.filter, filter, 1, attr);
+    define_native_function(vm.names.map, map, 1, attr);
 
     define_native_accessor(*vm.well_known_symbol_to_string_tag(), to_string_tag_getter, nullptr, Attribute::Configurable);
 
@@ -1096,4 +1097,54 @@ JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::filter)
     return filter_array;
 }
 
+// 23.2.3.19 %TypedArray%.prototype.map ( callbackfn [ , thisArg ] ), https://tc39.es/ecma262/#sec-%typedarray%.prototype.map
+JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::map)
+{
+    // 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 initial_length = typed_array->array_length();
+
+    // 4. If IsCallable(callbackfn) is false, throw a TypeError exception.
+    auto* callback_function = callback_from_args(global_object, "map");
+    if (!callback_function)
+        return {};
+
+    // 5. Let A be ? TypedArraySpeciesCreate(O, « 𝔽(len) »).
+    MarkedValueList arguments(vm.heap());
+    arguments.empend(initial_length);
+    auto* return_array = typed_array_species_create(global_object, *typed_array, move(arguments));
+    if (vm.exception())
+        return {};
+
+    auto this_value = vm.argument(1);
+
+    // 6. Let k be 0.
+    // 7. Repeat, while k < len,
+    for (size_t i = 0; i < initial_length; ++i) {
+        // a. Let Pk be ! ToString(𝔽(k)).
+        // b. Let kValue be ! Get(O, Pk).
+        auto value = typed_array->get(i);
+
+        // c. Let mappedValue be ? Call(callbackfn, thisArg, « kValue, 𝔽(k), O »).
+        auto mapped_value = vm.call(*callback_function, this_value, value, Value((i32)i), typed_array);
+        if (vm.exception())
+            return {};
+
+        // d. Perform ? Set(A, Pk, mappedValue, true).
+        return_array->set(i, mapped_value, true);
+        if (vm.exception())
+            return {};
+
+        // e. Set k to k + 1.
+    }
+
+    // 8. Return A.
+    return return_array;
+}
+
 }

Userland/Libraries/LibJS/Runtime/TypedArrayPrototype.h

@@ -45,6 +45,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(reverse);
     JS_DECLARE_NATIVE_FUNCTION(copy_within);
     JS_DECLARE_NATIVE_FUNCTION(filter);
+    JS_DECLARE_NATIVE_FUNCTION(map);
 };
 
 }

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

@@ -0,0 +1,259 @@
+const TYPED_ARRAYS = [
+    Uint8Array,
+    Uint8ClampedArray,
+    Uint16Array,
+    Uint32Array,
+    Int8Array,
+    Int16Array,
+    Int32Array,
+    Float32Array,
+    Float64Array,
+];
+
+const BIGINT_TYPED_ARRAYS = [BigUint64Array, BigInt64Array];
+
+test("length is 1", () => {
+    TYPED_ARRAYS.forEach(T => {
+        expect(T.prototype.map).toHaveLength(1);
+    });
+
+    BIGINT_TYPED_ARRAYS.forEach(T => {
+        expect(T.prototype.map).toHaveLength(1);
+    });
+});
+
+describe("errors", () => {
+    function argumentErrorTests(T) {
+        test(`requires at least one argument (${T.name})`, () => {
+            expect(() => {
+                new T().map();
+            }).toThrowWithMessage(
+                TypeError,
+                "TypedArray.prototype.map() requires at least one argument"
+            );
+        });
+
+        test(`callback must be a function (${T.name})`, () => {
+            expect(() => {
+                new T().map(undefined);
+            }).toThrowWithMessage(TypeError, "undefined is not a function");
+        });
+    }
+
+    TYPED_ARRAYS.forEach(T => argumentErrorTests(T));
+    BIGINT_TYPED_ARRAYS.forEach(T => argumentErrorTests(T));
+
+    test("throws if mappedValue is not the same type of the typed array", () => {
+        TYPED_ARRAYS.forEach(T => {
+            let callbackCalled = 0;
+            let result;
+
+            expect(() => {
+                result = new T([1, 2, 3]).map((value, index) => {
+                    callbackCalled++;
+                    return index % 2 === 0 ? 1n : 1;
+                });
+            }).toThrowWithMessage(TypeError, "Cannot convert BigInt to number");
+
+            expect(callbackCalled).toBe(1);
+            expect(result).toBeUndefined();
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            let callbackCalled = 0;
+            let result;
+
+            expect(() => {
+                result = new T([1n, 2n, 3n]).map((value, index) => {
+                    callbackCalled++;
+                    return index % 2 === 0 ? 1 : 1n;
+                });
+            }).toThrowWithMessage(TypeError, "Cannot convert number to BigInt");
+
+            expect(callbackCalled).toBe(1);
+            expect(result).toBeUndefined();
+        });
+    });
+
+    test("Symbol.species returns a typed array with a different content type", () => {
+        TYPED_ARRAYS.forEach(T => {
+            class TypedArray extends T {
+                static get [Symbol.species]() {
+                    return BigUint64Array;
+                }
+            }
+
+            let result;
+
+            expect(() => {
+                result = new TypedArray().map(() => {});
+            }).toThrowWithMessage(TypeError, `Can't create BigUint64Array from ${T.name}`);
+
+            expect(result).toBeUndefined();
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            class TypedArray extends T {
+                static get [Symbol.species]() {
+                    return Uint32Array;
+                }
+            }
+
+            let result;
+
+            expect(() => {
+                result = new TypedArray().map(() => {});
+            }).toThrowWithMessage(TypeError, `Can't create Uint32Array from ${T.name}`);
+
+            expect(result).toBeUndefined();
+        });
+    });
+
+    test("Symbol.species doesn't return a typed array", () => {
+        TYPED_ARRAYS.forEach(T => {
+            class TypedArray extends T {
+                static get [Symbol.species]() {
+                    return Array;
+                }
+            }
+
+            let result;
+
+            expect(() => {
+                result = new TypedArray().map(() => {});
+            }).toThrowWithMessage(TypeError, "Not a TypedArray object");
+
+            expect(result).toBeUndefined();
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            class TypedArray extends T {
+                static get [Symbol.species]() {
+                    return Array;
+                }
+            }
+
+            let result;
+
+            expect(() => {
+                result = new TypedArray().map(() => {});
+            }).toThrowWithMessage(TypeError, "Not a TypedArray object");
+
+            expect(result).toBeUndefined();
+        });
+    });
+});
+
+describe("normal behaviour", () => {
+    test("never calls callback with empty array", () => {
+        TYPED_ARRAYS.forEach(T => {
+            let callbackCalled = 0;
+            expect(
+                new T([]).map(() => {
+                    callbackCalled++;
+                })
+            ).toHaveLength(0);
+            expect(callbackCalled).toBe(0);
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            let callbackCalled = 0;
+            expect(
+                new T([]).map(() => {
+                    callbackCalled++;
+                })
+            ).toHaveLength(0);
+            expect(callbackCalled).toBe(0);
+        });
+    });
+
+    test("calls callback once for every item", () => {
+        TYPED_ARRAYS.forEach(T => {
+            let callbackCalled = 0;
+            expect(
+                new T([1, 2, 3]).map(value => {
+                    callbackCalled++;
+                    // NOTE: This is just to prevent a conversion exception.
+                    return value;
+                })
+            ).toHaveLength(3);
+            expect(callbackCalled).toBe(3);
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            let callbackCalled = 0;
+            expect(
+                new T([1n, 2n, 3n]).map(value => {
+                    callbackCalled++;
+                    // NOTE: This is just to prevent a conversion exception.
+                    return value;
+                })
+            ).toHaveLength(3);
+            expect(callbackCalled).toBe(3);
+        });
+    });
+
+    test("can map based on callback return value", () => {
+        TYPED_ARRAYS.forEach(T => {
+            const squaredNumbers = new T([0, 1, 2, 3, 4]).map(x => x ** 2);
+            expect(squaredNumbers).toHaveLength(5);
+            expect(squaredNumbers[0]).toBe(0);
+            expect(squaredNumbers[1]).toBe(1);
+            expect(squaredNumbers[2]).toBe(4);
+            expect(squaredNumbers[3]).toBe(9);
+            expect(squaredNumbers[4]).toBe(16);
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            const squaredNumbers = new T([0n, 1n, 2n, 3n, 4n]).map(x => x ** 2n);
+            expect(squaredNumbers).toHaveLength(5);
+            expect(squaredNumbers[0]).toBe(0n);
+            expect(squaredNumbers[1]).toBe(1n);
+            expect(squaredNumbers[2]).toBe(4n);
+            expect(squaredNumbers[3]).toBe(9n);
+            expect(squaredNumbers[4]).toBe(16n);
+        });
+    });
+
+    test("Symbol.species returns a typed array with a matching content type", () => {
+        TYPED_ARRAYS.forEach(T => {
+            class TypedArray extends T {
+                static get [Symbol.species]() {
+                    return Uint32Array;
+                }
+            }
+
+            let result;
+
+            expect(() => {
+                result = new TypedArray([1, 2, 3]).map(value => value + 2);
+            }).not.toThrowWithMessage(TypeError, `Can't create Uint32Array from ${T.name}`);
+
+            expect(result).toBeInstanceOf(Uint32Array);
+            expect(result).toHaveLength(3);
+            expect(result[0]).toBe(3);
+            expect(result[1]).toBe(4);
+            expect(result[2]).toBe(5);
+        });
+
+        BIGINT_TYPED_ARRAYS.forEach(T => {
+            class TypedArray extends T {
+                static get [Symbol.species]() {
+                    return BigUint64Array;
+                }
+            }
+
+            let result;
+
+            expect(() => {
+                result = new TypedArray([1n, 2n, 3n]).map(value => value + 2n);
+            }).not.toThrowWithMessage(TypeError, `Can't create BigUint64Array from ${T.name}`);
+
+            expect(result).toBeInstanceOf(BigUint64Array);
+            expect(result).toHaveLength(3);
+            expect(result[0]).toBe(3n);
+            expect(result[1]).toBe(4n);
+            expect(result[2]).toBe(5n);
+        });
+    });
+});