LibJS: Implement most of the Reflect object

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/79b829637e0
Pull-request: https://github.com/SerenityOS/serenity/pull/2047
Reviewed-by: https://github.com/awesomekling

Libraries/LibJS/AST.cpp

@@ -1087,11 +1087,17 @@ PropertyName MemberExpression::computed_property_name(Interpreter& interpreter)
     auto index = m_property->execute(interpreter);
     if (interpreter.exception())
         return {};
+
     ASSERT(!index.is_empty());
-    // FIXME: What about non-integer numbers tho.
-    if (index.is_number() && index.to_i32() >= 0)
-        return PropertyName(index.to_i32());
-    return PropertyName(index.to_string());
+
+    if (!index.to_number().is_finite_number())
+        return PropertyName(index.to_string());
+
+    auto index_as_double = index.to_double();
+    if (index_as_double < 0 || (i32)index_as_double != index_as_double)
+        return PropertyName(index.to_string());
+
+    return PropertyName(index.to_i32());
 }
 
 String MemberExpression::to_string_approximation() const

Libraries/LibJS/Interpreter.cpp

@@ -208,6 +208,30 @@ Value Interpreter::call(Function& function, Value this_value, Optional<MarkedVal
     return result;
 }
 
+Value Interpreter::construct(Function& function, Function& new_target, Optional<MarkedValueList> arguments)
+{
+    auto& call_frame = push_call_frame();
+    call_frame.function_name = function.name();
+    if (arguments.has_value())
+        call_frame.arguments = arguments.value().values();
+    call_frame.environment = function.create_environment();
+
+    auto* new_object = Object::create_empty(*this, global_object());
+    auto prototype = new_target.get("prototype");
+    if (prototype.is_object())
+        new_object->set_prototype(&prototype.as_object());
+    call_frame.this_value = new_object;
+    auto result = function.construct(*this);
+
+    pop_call_frame();
+
+    if (exception())
+        return {};
+    if (result.is_object())
+        return result;
+    return new_object;
+}
+
 Value Interpreter::throw_exception(Exception* exception)
 {
     if (exception->value().is_object() && exception->value().as_object().is_error()) {

Libraries/LibJS/Interpreter.h

@@ -104,6 +104,7 @@ public:
     void exit_scope(const ScopeNode&);
 
     Value call(Function&, Value this_value = {}, Optional<MarkedValueList> arguments = {});
+    Value construct(Function&, Function& new_target, Optional<MarkedValueList> arguments = {});
 
     CallFrame& push_call_frame()
     {

Libraries/LibJS/Makefile

@@ -39,6 +39,7 @@ OBJS = \
     Runtime/ObjectPrototype.o \
     Runtime/PrimitiveString.o \
     Runtime/Reference.o \
+    Runtime/ReflectObject.o \
     Runtime/ScriptFunction.o \
     Runtime/Shape.o \
     Runtime/StringConstructor.o \

Libraries/LibJS/Runtime/GlobalObject.cpp

@@ -49,6 +49,7 @@
 #include <LibJS/Runtime/Object.h>
 #include <LibJS/Runtime/ObjectConstructor.h>
 #include <LibJS/Runtime/ObjectPrototype.h>
+#include <LibJS/Runtime/ReflectObject.h>
 #include <LibJS/Runtime/Shape.h>
 #include <LibJS/Runtime/StringConstructor.h>
 #include <LibJS/Runtime/StringPrototype.h>
@@ -97,6 +98,7 @@ void GlobalObject::initialize()
     put("globalThis", this, attr);
     put("console", heap().allocate<ConsoleObject>(), attr);
     put("Math", heap().allocate<MathObject>(), attr);
+    put("Reflect", heap().allocate<ReflectObject>(), attr);
 
     add_constructor("Array", m_array_constructor, *m_array_prototype);
     add_constructor("Boolean", m_boolean_constructor, *m_boolean_prototype);

Libraries/LibJS/Runtime/Object.cpp

@@ -108,7 +108,7 @@ Value Object::get_own_property(const Object& this_object, const FlyString& prope
     return value_here;
 }
 
-Value Object::get_enumerable_own_properties(const Object& this_object, GetOwnPropertyMode kind) const
+Value Object::get_own_properties(const Object& this_object, GetOwnPropertyMode kind, u8 attributes) const
 {
     auto* properties_array = Array::create(interpreter().global_object());
 
@@ -152,7 +152,7 @@ Value Object::get_enumerable_own_properties(const Object& this_object, GetOwnPro
     }
 
     for (auto& it : this_object.shape().property_table_ordered()) {
-        if (it.value.attributes & Attribute::Enumerable) {
+        if (it.value.attributes & attributes) {
             size_t offset = it.value.offset + property_index;
 
             if (kind == GetOwnPropertyMode::Key) {
@@ -171,13 +171,42 @@ Value Object::get_enumerable_own_properties(const Object& this_object, GetOwnPro
     return properties_array;
 }
 
+Value Object::get_own_property_descriptor(const FlyString& property_name) const
+{
+    auto metadata = shape().lookup(property_name);
+    if (!metadata.has_value())
+        return js_undefined();
+    auto value = get(property_name);
+    if (interpreter().exception())
+        return {};
+    auto* descriptor = Object::create_empty(interpreter(), interpreter().global_object());
+    descriptor->put("value", value.value_or(js_undefined()));
+    descriptor->put("writable", Value(!!(metadata.value().attributes & Attribute::Writable)));
+    descriptor->put("enumerable", Value(!!(metadata.value().attributes & Attribute::Enumerable)));
+    descriptor->put("configurable", Value(!!(metadata.value().attributes & Attribute::Configurable)));
+    return descriptor;
+}
+
 void Object::set_shape(Shape& new_shape)
 {
     m_storage.resize(new_shape.property_count());
     m_shape = &new_shape;
 }
 
-bool Object::put_own_property(Object& this_object, const FlyString& property_name, u8 attributes, Value value, PutOwnPropertyMode mode)
+bool Object::define_property(const FlyString& property_name, const Object& descriptor, bool throw_exceptions)
+{
+    auto value = descriptor.get("value");
+    u8 configurable = descriptor.get("configurable").value_or(Value(false)).to_boolean() * Attribute::Configurable;
+    u8 enumerable = descriptor.get("enumerable").value_or(Value(false)).to_boolean() * Attribute::Enumerable;
+    u8 writable = descriptor.get("writable").value_or(Value(false)).to_boolean() * Attribute::Writable;
+    u8 attributes = configurable | enumerable | writable;
+
+    dbg() << "Defining new property " << property_name << " with descriptor { " << configurable << ", " << enumerable << ", " << writable << ", attributes=" << attributes << " }";
+
+    return put_own_property(*this, property_name, attributes, value, PutOwnPropertyMode::DefineProperty, throw_exceptions);
+}
+
+bool Object::put_own_property(Object& this_object, const FlyString& property_name, u8 attributes, Value value, PutOwnPropertyMode mode, bool throw_exceptions)
 {
     auto metadata = shape().lookup(property_name);
     bool new_property = !metadata.has_value();
@@ -195,7 +224,8 @@ bool Object::put_own_property(Object& this_object, const FlyString& property_nam
 
     if (!new_property && mode == PutOwnPropertyMode::DefineProperty && !(metadata.value().attributes & Attribute::Configurable) && attributes != metadata.value().attributes) {
         dbg() << "Disallow reconfig of non-configurable property";
-        interpreter().throw_exception<TypeError>(String::format("Cannot redefine property '%s'", property_name.characters()));
+        if (throw_exceptions)
+            interpreter().throw_exception<TypeError>(String::format("Cannot redefine property '%s'", property_name.characters()));
         return false;
     }
 

Libraries/LibJS/Runtime/Object.h

@@ -46,6 +46,17 @@ public:
     explicit Object(Object* prototype);
     virtual ~Object();
 
+    enum class GetOwnPropertyMode {
+        Key,
+        Value,
+        KeyAndValue,
+    };
+
+    enum class PutOwnPropertyMode {
+        Put,
+        DefineProperty,
+    };
+
     Shape& shape() { return *m_shape; }
     const Shape& shape() const { return *m_shape; }
 
@@ -60,20 +71,11 @@ public:
     bool put(PropertyName, Value, u8 attributes = default_attributes);
 
     Value get_own_property(const Object& this_object, const FlyString& property_name) const;
+    Value get_own_properties(const Object& this_object, GetOwnPropertyMode, u8 attributes = Attribute::Configurable | Attribute::Enumerable | Attribute::Writable) const;
+    Value get_own_property_descriptor(const FlyString& property_name) const;
 
-    enum class GetOwnPropertyMode {
-        Key,
-        Value,
-        KeyAndValue,
-    };
-    Value get_enumerable_own_properties(const Object& this_object, GetOwnPropertyMode) const;
-
-    enum class PutOwnPropertyMode {
-        Put,
-        DefineProperty,
-    };
-
-    bool put_own_property(Object& this_object, const FlyString& property_name, u8 attributes, Value, PutOwnPropertyMode);
+    bool define_property(const FlyString& property_name, const Object& descriptor, bool throw_exceptions = true);
+    bool put_own_property(Object& this_object, const FlyString& property_name, u8 attributes, Value, PutOwnPropertyMode, bool throw_exceptions = true);
 
     bool put_native_function(const FlyString& property_name, AK::Function<Value(Interpreter&)>, i32 length = 0, u8 attribute = default_attributes);
     bool put_native_property(const FlyString& property_name, AK::Function<Value(Interpreter&)> getter, AK::Function<void(Interpreter&, Value)> setter, u8 attribute = default_attributes);

Libraries/LibJS/Runtime/ObjectConstructor.cpp

@@ -108,47 +108,23 @@ Value ObjectConstructor::set_prototype_of(Interpreter& interpreter)
 
 Value ObjectConstructor::get_own_property_descriptor(Interpreter& interpreter)
 {
-    if (interpreter.argument_count() < 2)
-        return interpreter.throw_exception<TypeError>("Object.getOwnPropertyDescriptor() needs 2 arguments");
-    if (!interpreter.argument(0).is_object())
-        return interpreter.throw_exception<TypeError>("Object argument is not an object");
-    auto& object = interpreter.argument(0).as_object();
-    auto metadata = object.shape().lookup(interpreter.argument(1).to_string());
-    if (!metadata.has_value())
-        return js_undefined();
-
-    auto value = object.get(interpreter.argument(1).to_string()).value_or(js_undefined());
+    auto* object = interpreter.argument(0).to_object(interpreter.heap());
     if (interpreter.exception())
         return {};
-
-    auto* descriptor = Object::create_empty(interpreter, interpreter.global_object());
-    descriptor->put("configurable", Value(!!(metadata.value().attributes & Attribute::Configurable)));
-    descriptor->put("enumerable", Value(!!(metadata.value().attributes & Attribute::Enumerable)));
-    descriptor->put("writable", Value(!!(metadata.value().attributes & Attribute::Writable)));
-    descriptor->put("value", value);
-    return descriptor;
+    auto property_key = interpreter.argument(1).to_string();
+    return object->get_own_property_descriptor(property_key);
 }
 
 Value ObjectConstructor::define_property(Interpreter& interpreter)
 {
-    if (interpreter.argument_count() < 3)
-        return interpreter.throw_exception<TypeError>("Object.defineProperty() needs 3 arguments");
     if (!interpreter.argument(0).is_object())
         return interpreter.throw_exception<TypeError>("Object argument is not an object");
     if (!interpreter.argument(2).is_object())
         return interpreter.throw_exception<TypeError>("Descriptor argument is not an object");
     auto& object = interpreter.argument(0).as_object();
+    auto property_key = interpreter.argument(1).to_string();
     auto& descriptor = interpreter.argument(2).as_object();
-
-    auto value = descriptor.get("value");
-    u8 configurable = descriptor.get("configurable").value_or(Value(false)).to_boolean() * Attribute::Configurable;
-    u8 enumerable = descriptor.get("enumerable").value_or(Value(false)).to_boolean() * Attribute::Enumerable;
-    u8 writable = descriptor.get("writable").value_or(Value(false)).to_boolean() * Attribute::Writable;
-    u8 attributes = configurable | enumerable | writable;
-
-    dbg() << "Defining new property " << interpreter.argument(1).to_string() << " with descriptor { " << configurable << ", " << enumerable << ", " << writable << ", attributes=" << attributes << " }";
-
-    object.put_own_property(object, interpreter.argument(1).to_string(), attributes, value, PutOwnPropertyMode::DefineProperty);
+    object.define_property(property_key, descriptor);
     return &object;
 }
 
@@ -177,7 +153,7 @@ Value ObjectConstructor::keys(Interpreter& interpreter)
     if (interpreter.exception())
         return {};
 
-    return obj_arg->get_enumerable_own_properties(*obj_arg, GetOwnPropertyMode::Key);
+    return obj_arg->get_own_properties(*obj_arg, GetOwnPropertyMode::Key, Attribute::Enumerable);
 }
 
 Value ObjectConstructor::values(Interpreter& interpreter)
@@ -189,7 +165,7 @@ Value ObjectConstructor::values(Interpreter& interpreter)
     if (interpreter.exception())
         return {};
 
-    return obj_arg->get_enumerable_own_properties(*obj_arg, GetOwnPropertyMode::Value);
+    return obj_arg->get_own_properties(*obj_arg, GetOwnPropertyMode::Value, Attribute::Enumerable);
 }
 
 Value ObjectConstructor::entries(Interpreter& interpreter)
@@ -201,7 +177,7 @@ Value ObjectConstructor::entries(Interpreter& interpreter)
     if (interpreter.exception())
         return {};
 
-    return obj_arg->get_enumerable_own_properties(*obj_arg, GetOwnPropertyMode::KeyAndValue);
+    return obj_arg->get_own_properties(*obj_arg, GetOwnPropertyMode::KeyAndValue, Attribute::Enumerable);
 }
 
 }

Libraries/LibJS/Runtime/ReflectObject.cpp

@@ -0,0 +1,251 @@
+/*
+ * Copyright (c) 2020, Linus Groh <mail@linusgroh.de>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Function.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/Error.h>
+#include <LibJS/Runtime/Function.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/NativeFunction.h>
+#include <LibJS/Runtime/ReflectObject.h>
+
+namespace JS {
+
+static Object* get_target_object_from(Interpreter& interpreter, const String& name)
+{
+    auto target = interpreter.argument(0);
+    if (!target.is_object()) {
+        interpreter.throw_exception<TypeError>(String::format("First argument of Reflect.%s() must be an object", name.characters()));
+        return nullptr;
+    }
+    return static_cast<Object*>(&target.as_object());
+}
+
+static Function* get_target_function_from(Interpreter& interpreter, const String& name)
+{
+    auto target = interpreter.argument(0);
+    if (!target.is_object() || !target.as_object().is_function()) {
+        interpreter.throw_exception<TypeError>(String::format("First argument of Reflect.%s() must be a function", name.characters()));
+        return nullptr;
+    }
+    return static_cast<Function*>(&target.as_object());
+}
+
+static void prepare_arguments_list(Interpreter& interpreter, Value value, MarkedValueList* arguments)
+{
+    if (!value.is_object()) {
+        interpreter.throw_exception<TypeError>("Arguments list must be an object");
+        return;
+    }
+    auto& arguments_list = value.as_object();
+    auto length_property = arguments_list.get("length");
+    if (interpreter.exception())
+        return;
+    auto length = length_property.to_size_t();
+    for (size_t i = 0; i < length; ++i) {
+        auto element = arguments_list.get(String::number(i));
+        if (interpreter.exception())
+            return;
+        arguments->append(element.value_or(js_undefined()));
+    }
+}
+
+ReflectObject::ReflectObject()
+    : Object(interpreter().global_object().object_prototype())
+{
+    u8 attr = Attribute::Writable | Attribute::Configurable;
+    put_native_function("apply", apply, 3, attr);
+    put_native_function("construct", construct, 2, attr);
+    put_native_function("defineProperty", define_property, 3, attr);
+    put_native_function("deleteProperty", delete_property, 2, attr);
+    put_native_function("get", get, 2, attr);
+    put_native_function("getOwnPropertyDescriptor", get_own_property_descriptor, 2, attr);
+    put_native_function("getPrototypeOf", get_prototype_of, 1, attr);
+    put_native_function("has", has, 2, attr);
+    put_native_function("isExtensible", is_extensible, 1, attr);
+    put_native_function("ownKeys", own_keys, 1, attr);
+    put_native_function("preventExtensions", prevent_extensions, 1, attr);
+    put_native_function("set", set, 3, attr);
+    put_native_function("setPrototypeOf", set_prototype_of, 2, attr);
+}
+
+ReflectObject::~ReflectObject()
+{
+}
+
+Value ReflectObject::apply(Interpreter& interpreter)
+{
+    auto* target = get_target_function_from(interpreter, "apply");
+    if (!target)
+        return {};
+    auto this_arg = interpreter.argument(1);
+    MarkedValueList arguments(interpreter.heap());
+    prepare_arguments_list(interpreter, interpreter.argument(2), &arguments);
+    if (interpreter.exception())
+        return {};
+    return interpreter.call(*target, this_arg, move(arguments));
+}
+
+Value ReflectObject::construct(Interpreter& interpreter)
+{
+    auto* target = get_target_function_from(interpreter, "construct");
+    if (!target)
+        return {};
+    MarkedValueList arguments(interpreter.heap());
+    prepare_arguments_list(interpreter, interpreter.argument(1), &arguments);
+    if (interpreter.exception())
+        return {};
+    auto* new_target = target;
+    if (interpreter.argument_count() > 2) {
+        auto new_target_value = interpreter.argument(2);
+        if (!new_target_value.is_object()
+            || !new_target_value.as_object().is_function()
+            || (new_target_value.as_object().is_native_function() && !static_cast<NativeFunction&>(new_target_value.as_object()).has_constructor())) {
+            interpreter.throw_exception<TypeError>("Optional third argument of Reflect.construct() must be a constructor");
+            return {};
+        }
+        new_target = static_cast<Function*>(&new_target_value.as_object());
+    }
+    return interpreter.construct(*target, *new_target, move(arguments));
+}
+
+Value ReflectObject::define_property(Interpreter& interpreter)
+{
+    auto* target = get_target_object_from(interpreter, "defineProperty");
+    if (!target)
+        return {};
+    if (!interpreter.argument(2).is_object())
+        return interpreter.throw_exception<TypeError>("Descriptor argument is not an object");
+    auto property_key = interpreter.argument(1).to_string();
+    auto& descriptor = interpreter.argument(2).as_object();
+    auto success = target->define_property(property_key, descriptor, false);
+    return Value(success);
+}
+
+Value ReflectObject::delete_property(Interpreter& interpreter)
+{
+    auto* target = get_target_object_from(interpreter, "deleteProperty");
+    if (!target)
+        return {};
+
+    auto property_key = interpreter.argument(1);
+    PropertyName property = PropertyName(property_key.to_string());
+    if (property_key.to_number().is_finite_number()) {
+        auto property_key_as_double = property_key.to_double();
+        if (property_key_as_double >= 0 && (i32)property_key_as_double == property_key_as_double)
+            property = PropertyName(property_key_as_double);
+    }
+    return target->delete_property(property);
+}
+
+Value ReflectObject::get(Interpreter& interpreter)
+{
+    // FIXME: There's a third argument, receiver, for getters - use it once we have those.
+    auto* target = get_target_object_from(interpreter, "get");
+    if (!target)
+        return {};
+    auto property_key = interpreter.argument(1).to_string();
+    return target->get(property_key).value_or(js_undefined());
+}
+
+Value ReflectObject::get_own_property_descriptor(Interpreter& interpreter)
+{
+    auto* target = get_target_object_from(interpreter, "getOwnPropertyDescriptor");
+    if (!target)
+        return {};
+    auto property_key = interpreter.argument(1).to_string();
+    return target->get_own_property_descriptor(property_key);
+}
+
+Value ReflectObject::get_prototype_of(Interpreter& interpreter)
+{
+    auto* target = get_target_object_from(interpreter, "getPrototypeOf");
+    if (!target)
+        return {};
+    return target->prototype();
+}
+
+Value ReflectObject::has(Interpreter& interpreter)
+{
+    auto* target = get_target_object_from(interpreter, "has");
+    if (!target)
+        return {};
+    auto property_key = interpreter.argument(1).to_string();
+    return Value(target->has_property(property_key));
+}
+
+Value ReflectObject::is_extensible(Interpreter&)
+{
+    // FIXME: For this to be useful we need one of these:
+    // Object.seal(), Object.freeze(), Reflect.preventExtensions()
+    // For now we just return true, as that's always the case.
+    return Value(true);
+}
+
+Value ReflectObject::own_keys(Interpreter& interpreter)
+{
+    auto* target = get_target_object_from(interpreter, "ownKeys");
+    if (!target)
+        return {};
+    return target->get_own_properties(*target, GetOwnPropertyMode::Key);
+}
+
+Value ReflectObject::prevent_extensions(Interpreter&)
+{
+    // FIXME: Implement me :^)
+    ASSERT_NOT_REACHED();
+}
+
+Value ReflectObject::set(Interpreter& interpreter)
+{
+    // FIXME: There's a fourth argument, receiver, for setters - use it once we have those.
+    auto* target = get_target_object_from(interpreter, "set");
+    if (!target)
+        return {};
+    auto property_key = interpreter.argument(1).to_string();
+    auto value = interpreter.argument(2);
+    return Value(target->put(property_key, value));
+}
+
+Value ReflectObject::set_prototype_of(Interpreter& interpreter)
+{
+    auto* target = get_target_object_from(interpreter, "setPrototypeOf");
+    if (!target)
+        return {};
+    auto prototype_value = interpreter.argument(1);
+    if (!prototype_value.is_object() && !prototype_value.is_null()) {
+        interpreter.throw_exception<TypeError>("Prototype must be an object or null");
+        return {};
+    }
+    Object* prototype = nullptr;
+    if (!prototype_value.is_null())
+        prototype = const_cast<Object*>(&prototype_value.as_object());
+    target->set_prototype(prototype);
+    // FIXME: Needs to return false for prototype chain cycles and non-extensible objects (don't have those yet).
+    return Value(true);
+}
+
+}

Libraries/LibJS/Runtime/ReflectObject.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2020, Linus Groh <mail@linusgroh.de>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+class ReflectObject final : public Object {
+public:
+    ReflectObject();
+    virtual ~ReflectObject() override;
+
+private:
+    virtual const char* class_name() const override { return "ReflectObject"; }
+
+    static Value apply(Interpreter&);
+    static Value construct(Interpreter&);
+    static Value define_property(Interpreter&);
+    static Value delete_property(Interpreter&);
+    static Value get(Interpreter&);
+    static Value get_own_property_descriptor(Interpreter&);
+    static Value get_prototype_of(Interpreter&);
+    static Value has(Interpreter&);
+    static Value is_extensible(Interpreter&);
+    static Value own_keys(Interpreter&);
+    static Value prevent_extensions(Interpreter&);
+    static Value set(Interpreter&);
+    static Value set_prototype_of(Interpreter&);
+};
+
+}

Libraries/LibJS/Runtime/Value.cpp

@@ -38,6 +38,9 @@
 #include <LibJS/Runtime/Value.h>
 #include <math.h>
 
+// 2 ** 53 - 1
+#define MAX_ARRAY_LIKE_INDEX 9007199254740991.0
+
 namespace JS {
 
 bool Value::is_array() const
@@ -190,7 +193,7 @@ size_t Value::to_size_t() const
     auto number = to_number();
     if (number.is_nan() || number.as_double() <= 0)
         return 0;
-    return min(number.to_i32(), (i32)pow(2, 53) - 1);
+    return min((double)number.to_i32(), MAX_ARRAY_LIKE_INDEX);
 }
 
 Value greater_than(Interpreter&, Value lhs, Value rhs)

Libraries/LibJS/Tests/Reflect.apply.js

@@ -0,0 +1,37 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.apply.length === 3);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.apply(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.apply() must be a function"
+        });
+
+        assertThrowsError(() => {
+            Reflect.apply(() => {}, undefined, value);
+        }, {
+            error: TypeError,
+            message: "Arguments list must be an object"
+        });
+    });
+
+    assert(Reflect.apply(String.prototype.charAt, "foo", [0]) === "f");
+    assert(Reflect.apply(Array.prototype.indexOf, ["hello", 123, "foo", "bar"], ["foo"]) === 2);
+
+    function Foo(foo) {
+        this.foo = foo;
+    }
+
+    var o = {};
+    assert(o.foo === undefined);
+    assert(Reflect.apply(Foo, o, ["bar"]) === undefined);
+    assert(o.foo === "bar");
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.construct.js

@@ -0,0 +1,54 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.construct.length === 2);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.construct(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.construct() must be a function"
+        });
+
+        assertThrowsError(() => {
+            Reflect.construct(() => {}, value);
+        }, {
+            error: TypeError,
+            message: "Arguments list must be an object"
+        });
+
+        assertThrowsError(() => {
+            Reflect.construct(() => {}, [], value);
+        }, {
+            error: TypeError,
+            message: "Optional third argument of Reflect.construct() must be a constructor"
+        });
+    });
+
+    var a = Reflect.construct(Array, [5]);
+    assert(a instanceof Array);
+    assert(a.length === 5);
+
+    var s = Reflect.construct(String, [123]);
+    assert(s instanceof String);
+    assert(s.length === 3);
+    assert(s.toString() === "123");
+
+    function Foo() {
+        this.name = "foo";
+    }
+    
+    function Bar() {
+        this.name = "bar";
+    }
+
+    var o = Reflect.construct(Foo, [], Bar);
+    assert(o.name === "foo");
+    assert(o instanceof Foo === false);
+    assert(o instanceof Bar === true);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.defineProperty.js

@@ -0,0 +1,59 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.defineProperty.length === 3);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.defineProperty(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.defineProperty() must be an object"
+        });
+
+        assertThrowsError(() => {
+            Reflect.defineProperty({}, "foo", value);
+        }, {
+            error: TypeError,
+            message: "Descriptor argument is not an object"
+        });
+    });
+
+    var o = {};
+
+    assert(Reflect.defineProperty(o, "foo", { value: 1, writable: false, enumerable: false }) === true);
+    assert(o.foo === 1);
+    o.foo = 2;
+    assert(o.foo === 1);
+
+    assert(Reflect.defineProperty(o, "bar", { value: "hi", writable: true, enumerable: true }) === true);
+    assert(o.bar === "hi");
+    o.bar = "ho";
+    assert(o.bar === "ho");
+
+    assert(Reflect.defineProperty(o, "bar", { value: "xx", enumerable: false }) === false);
+
+    var d = Reflect.getOwnPropertyDescriptor(o, "foo");
+    assert(d.configurable === false);
+    assert(d.enumerable === false);
+    assert(d.writable === false);
+    assert(d.value === 1);
+
+    d = Reflect.getOwnPropertyDescriptor(o, "bar");
+    assert(d.configurable === false);
+    assert(d.enumerable === true);
+    assert(d.writable === true);
+    assert(d.value === "ho");
+
+    assert(Reflect.defineProperty(o, "baz", { value: 9, configurable: true, writable: false }) === true);
+    assert(Reflect.defineProperty(o, "baz", { configurable: true, writable: true }) === true);
+
+    d = Reflect.getOwnPropertyDescriptor(o, "baz");
+    assert(d.configurable === true);
+    assert(d.writable === true);
+    assert(d.value === 9);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.deleteProperty.js

@@ -0,0 +1,47 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.deleteProperty.length === 2);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.deleteProperty(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.deleteProperty() must be an object"
+        });
+    });
+
+    assert(Reflect.deleteProperty({}) === true);
+    assert(Reflect.deleteProperty({}, "foo") === true);
+
+    var o = { foo: 1 };
+    assert(o.foo === 1);
+    assert(Reflect.deleteProperty(o, "foo") === true);
+    assert(o.foo === undefined);
+    assert(Reflect.deleteProperty(o, "foo") === true);
+    assert(o.foo === undefined);
+
+    Object.defineProperty(o, "bar", { value: 2, configurable: true, writable: false });
+    assert(Reflect.deleteProperty(o, "bar") === true);
+    assert(o.bar === undefined);
+
+    Object.defineProperty(o, "baz", { value: 3, configurable: false, writable: true });
+    assert(Reflect.deleteProperty(o, "baz") === false);
+    assert(o.baz === 3);
+
+    var a = [1, 2, 3];
+    assert(a.length === 3);
+    assert(a[0] === 1);
+    assert(a[1] === 2);
+    assert(a[2] === 3);
+    assert(Reflect.deleteProperty(a, 1) === true);
+    assert(a.length === 3);
+    assert(a[0] === 1);
+    assert(a[1] === undefined);
+    assert(a[2] === 3);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.get.js

@@ -0,0 +1,39 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.get.length === 2);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.get(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.get() must be an object"
+        });
+    });
+
+    assert(Reflect.get({}) === undefined);
+    assert(Reflect.get({ undefined: 1 }) === 1);
+    assert(Reflect.get({ foo: 1 }) === undefined);
+    assert(Reflect.get({ foo: 1 }, "foo") === 1);
+
+    assert(Reflect.get([]) === undefined);
+    assert(Reflect.get([1, 2, 3]) === undefined);
+    assert(Reflect.get([1, 2, 3], "0") === 1);
+    assert(Reflect.get([1, 2, 3], 0) === 1);
+    assert(Reflect.get([1, 2, 3], 1) === 2);
+    assert(Reflect.get([1, 2, 3], 2) === 3);
+    assert(Reflect.get([1, 2, 3], 4) === undefined);
+
+    assert(Reflect.get(new String()) === undefined);
+    assert(Reflect.get(new String(), 0) === undefined);
+    assert(Reflect.get(new String("foo"), "0") === "f");
+    assert(Reflect.get(new String("foo"), 0) === "f");
+    assert(Reflect.get(new String("foo"), 1) === "o");
+    assert(Reflect.get(new String("foo"), 2) === "o");
+    assert(Reflect.get(new String("foo"), 3) === undefined);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.getOwnPropertyDescriptor.js

@@ -0,0 +1,35 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.getOwnPropertyDescriptor.length === 2);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.getOwnPropertyDescriptor(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.getOwnPropertyDescriptor() must be an object"
+        });
+    });
+
+    assert(Reflect.getOwnPropertyDescriptor({}) === undefined);
+    assert(Reflect.getOwnPropertyDescriptor({}, "foo") === undefined);
+
+    var o = { foo: "bar" };
+    var d = Reflect.getOwnPropertyDescriptor(o, "foo");
+    assert(d.value === "bar");
+    assert(d.writable === true);
+    assert(d.enumerable === true);
+    assert(d.configurable === true);
+
+    var a = [];
+    d = Reflect.getOwnPropertyDescriptor(a, "length");
+    assert(d.value === 0);
+    assert(d.writable === true);
+    assert(d.enumerable === false);
+    assert(d.configurable === false);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.getPrototypeOf.js

@@ -0,0 +1,26 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.getPrototypeOf.length === 1);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.getPrototypeOf(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.getPrototypeOf() must be an object"
+        });
+    });
+
+    assert(Reflect.getPrototypeOf({}) === Object.prototype);
+    assert(Reflect.getPrototypeOf([]) === Array.prototype);
+    assert(Reflect.getPrototypeOf(new String()) === String.prototype);
+
+    var o = {};
+    Reflect.setPrototypeOf(o, { foo: "bar" });
+    assert(Reflect.getPrototypeOf(o).foo === "bar");
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.has.js

@@ -0,0 +1,42 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.has.length === 2);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.has(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.has() must be an object"
+        });
+    });
+
+    assert(Reflect.has({}) === false);
+    assert(Reflect.has({ undefined }) === true);
+    assert(Reflect.has({ 0: "1" }, "0") === true);
+    assert(Reflect.has({ foo: "bar" }, "foo") === true);
+    assert(Reflect.has({ bar: "baz" }, "foo") === false);
+    assert(Reflect.has({}, "toString") === true);
+
+    assert(Reflect.has([]) === false);
+    assert(Reflect.has([], 0) === false);
+    assert(Reflect.has([1, 2, 3], "0") === true);
+    assert(Reflect.has([1, 2, 3], 0) === true);
+    assert(Reflect.has([1, 2, 3], 1) === true);
+    assert(Reflect.has([1, 2, 3], 2) === true);
+    assert(Reflect.has([1, 2, 3], 3) === false);
+    assert(Reflect.has([], "pop") === true);
+
+    assert(Reflect.has(new String()) === false);
+    assert(Reflect.has(new String("foo"), "0") === true);
+    assert(Reflect.has(new String("foo"), 0) === true);
+    assert(Reflect.has(new String("foo"), 1) === true);
+    assert(Reflect.has(new String("foo"), 2) === true);
+    assert(Reflect.has(new String("foo"), 3) === false);
+    assert(Reflect.has(new String("foo"), "charAt") === true);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.ownKeys.js

@@ -0,0 +1,39 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.ownKeys.length === 1);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.ownKeys(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.ownKeys() must be an object"
+        });
+    });
+
+    var objectOwnKeys = Reflect.ownKeys({});
+    assert(objectOwnKeys.length === 0);
+
+    objectOwnKeys = Reflect.ownKeys({ foo: "bar", bar: "baz", 0: 42 });
+    assert(objectOwnKeys.length === 3);
+    assert(objectOwnKeys[0] === "0");
+    assert(objectOwnKeys[1] === "foo");
+    assert(objectOwnKeys[2] === "bar");
+
+    var arrayOwnKeys = Reflect.ownKeys([]);
+    assert(arrayOwnKeys.length === 1);
+    assert(arrayOwnKeys[0] === "length");
+
+    arrayOwnKeys = Reflect.ownKeys(["foo", [], 123, undefined]);
+    assert(arrayOwnKeys.length === 5);
+    assert(arrayOwnKeys[0] === "0");
+    assert(arrayOwnKeys[1] === "1");
+    assert(arrayOwnKeys[2] === "2");
+    assert(arrayOwnKeys[3] === "3");
+    assert(arrayOwnKeys[4] === "length");
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.set.js

@@ -0,0 +1,54 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.set.length === 3);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.set(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.set() must be an object"
+        });
+    });
+
+    assert(Reflect.set({}) === true);
+    assert(Reflect.set({}, "foo") === true);
+    assert(Reflect.set({}, "foo", "bar") === true);
+
+    var o = {};
+    assert(o.foo === undefined);
+    assert(Reflect.set(o, "foo", 1) === true);
+    assert(o.foo === 1);
+    assert(Reflect.set(o, "foo", 2) === true);
+    assert(o.foo === 2);
+
+    Object.defineProperty(o, "bar", { value: 2, configurable: true, writable: false });
+    assert(Reflect.set(o, "bar") === false);
+    assert(o.bar === 2);
+
+    Object.defineProperty(o, "baz", { value: 3, configurable: false, writable: true });
+    assert(Reflect.set(o, "baz") === true);
+    assert(o.baz === undefined);
+
+    var a = [];
+    assert(a.length === 0);
+    assert(Reflect.set(a, "0") === true);
+    assert(a.length === 1);
+    assert(a[0] === undefined);
+    assert(Reflect.set(a, 1, "foo") === true);
+    assert(a.length === 2);
+    assert(a[0] === undefined);
+    assert(a[1] === "foo");
+    assert(Reflect.set(a, 4, "bar") === true);
+    assert(a.length === 5);
+    assert(a[0] === undefined);
+    assert(a[1] === "foo");
+    assert(a[2] === undefined);
+    assert(a[3] === undefined);
+    assert(a[4] === "bar");
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Reflect.setPrototypeOf.js

@@ -0,0 +1,39 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.setPrototypeOf.length === 2);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.setPrototypeOf(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.setPrototypeOf() must be an object"
+        });
+        if (value === null)
+            return;
+        assertThrowsError(() => {
+            Reflect.setPrototypeOf({}, value);
+        }, {
+            error: TypeError,
+            message: "Prototype must be an object or null"
+        });
+    });
+
+    assert(Reflect.setPrototypeOf({}, null) === true);
+    assert(Reflect.setPrototypeOf({}, {}) === true);
+    assert(Reflect.setPrototypeOf({}, Object.prototype) === true);
+    assert(Reflect.setPrototypeOf({}, Array.prototype) === true);
+    assert(Reflect.setPrototypeOf({}, String.prototype) === true);
+    assert(Reflect.setPrototypeOf({}, Reflect.getPrototypeOf({})) === true);
+
+    var o = {};
+    assert(o.foo === undefined);
+    assert(Reflect.setPrototypeOf(o, { foo: "bar" }) === true);
+    assert(o.foo === "bar");
+
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}