1 files changed, 75 insertions, 0 deletions
diff --git a/Userland/Libraries/LibJS/Runtime/FunctionObject.h b/Userland/Libraries/LibJS/Runtime/FunctionObject.h
new file mode 100644
index 0000000000..66637bcec6
--- /dev/null
+++ b/Userland/Libraries/LibJS/Runtime/FunctionObject.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+class FunctionObject : public Object {
+    JS_OBJECT(Function, Object);
+
+public:
+    enum class ConstructorKind {
+        Base,
+        Derived,
+    };
+
+    virtual ~FunctionObject();
+    virtual void initialize(GlobalObject&) override { }
+
+    virtual Value call() = 0;
+    virtual Value construct(FunctionObject& new_target) = 0;
+    virtual const FlyString& name() const = 0;
+    virtual FunctionEnvironmentRecord* create_environment_record(FunctionObject&) = 0;
+
+    BoundFunction* bind(Value bound_this_value, Vector<Value> arguments);
+
+    Value bound_this() const { return m_bound_this; }
+
+    const Vector<Value>& bound_arguments() const { return m_bound_arguments; }
+
+    Value home_object() const { return m_home_object; }
+    void set_home_object(Value home_object) { m_home_object = home_object; }
+
+    ConstructorKind constructor_kind() const { return m_constructor_kind; };
+    void set_constructor_kind(ConstructorKind constructor_kind) { m_constructor_kind = constructor_kind; }
+
+    virtual bool is_strict_mode() const { return false; }
+
+    // [[Environment]]
+    // The Environment Record that the function was closed over.
+    // Used as the outer environment when evaluating the code of the function.
+    virtual EnvironmentRecord* environment() { return nullptr; }
+
+    enum class ThisMode : u8 {
+        Lexical,
+        Strict,
+        Global,
+    };
+
+    // [[ThisMode]]
+    ThisMode this_mode() const { return m_this_mode; }
+    void set_this_mode(ThisMode this_mode) { m_this_mode = this_mode; }
+
+protected:
+    virtual void visit_edges(Visitor&) override;
+
+    explicit FunctionObject(Object& prototype);
+    FunctionObject(Value bound_this, Vector<Value> bound_arguments, Object& prototype);
+
+private:
+    virtual bool is_function() const override { return true; }
+    Value m_bound_this;
+    Vector<Value> m_bound_arguments;
+    Value m_home_object;
+    ConstructorKind m_constructor_kind = ConstructorKind::Base;
+    ThisMode m_this_mode { ThisMode::Global };
+};
+
+}