LibWeb: Add XMLHttpRequest object :^)

This patch adds very basic XMLHttpRequest support to LibWeb. Here's an
example that currently works:

    var callback = function() { alert(this.responseText); }
    var xhr = new XMLHttpRequest();
    xhr.addEventListener("load", callback);
    xhr.open("GET", "http://serenityos.org/~kling/test/example.txt");
    xhr.send();

There are many limitations and bugs, but it's pretty dang awesome that
we have XHR. :^)

Libraries/LibJS/Runtime/GlobalObject.h

@@ -43,9 +43,11 @@ public:
     NumberConstructor* number_constructor() { return m_number_constructor; };
     ObjectConstructor* object_constructor() { return m_object_constructor; }
 
+protected:
+    virtual void visit_children(Visitor&) override;
+
 private:
     virtual const char* class_name() const override { return "GlobalObject"; }
-    virtual void visit_children(Visitor&) override;
 
     static Value gc(Interpreter&);
     static Value is_nan(Interpreter&);

Libraries/LibWeb/Bindings/WindowObject.cpp

@@ -32,6 +32,8 @@
 #include <LibWeb/Bindings/DocumentWrapper.h>
 #include <LibWeb/Bindings/NavigatorObject.h>
 #include <LibWeb/Bindings/WindowObject.h>
+#include <LibWeb/Bindings/XMLHttpRequestConstructor.h>
+#include <LibWeb/Bindings/XMLHttpRequestPrototype.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Window.h>
 
@@ -50,12 +52,24 @@ WindowObject::WindowObject(Window& impl)
     put_native_function("cancelAnimationFrame", cancel_animation_frame, 1);
 
     put("navigator", heap().allocate<NavigatorObject>());
+
+    m_xhr_prototype = heap().allocate<XMLHttpRequestPrototype>();
+    m_xhr_constructor = heap().allocate<XMLHttpRequestConstructor>();
+    m_xhr_constructor->put("prototype", m_xhr_prototype);
+    put("XMLHttpRequest", m_xhr_constructor);
 }
 
 WindowObject::~WindowObject()
 {
 }
 
+void WindowObject::visit_children(Visitor& visitor)
+{
+    GlobalObject::visit_children(visitor);
+    visitor.visit(m_xhr_constructor);
+    visitor.visit(m_xhr_prototype);
+}
+
 static Window* impl_from(JS::Interpreter& interpreter)
 {
     auto* this_object = interpreter.this_value().to_object(interpreter.heap());

Libraries/LibWeb/Bindings/WindowObject.h

@@ -32,7 +32,7 @@
 namespace Web {
 namespace Bindings {
 
-class WindowObject : public JS::GlobalObject {
+class WindowObject final : public JS::GlobalObject {
 public:
     explicit WindowObject(Window&);
     virtual ~WindowObject() override;
@@ -40,8 +40,12 @@ public:
     Window& impl() { return *m_impl; }
     const Window& impl() const { return *m_impl; }
 
+    XMLHttpRequestPrototype* xhr_prototype() { return m_xhr_prototype; }
+    XMLHttpRequestConstructor* xhr_constructor() { return m_xhr_constructor; }
+
 private:
     virtual const char* class_name() const override { return "WindowObject"; }
+    virtual void visit_children(Visitor&) override;
 
     static JS::Value document_getter(JS::Interpreter&);
     static void document_setter(JS::Interpreter&, JS::Value);
@@ -53,6 +57,9 @@ private:
     static JS::Value cancel_animation_frame(JS::Interpreter&);
 
     NonnullRefPtr<Window> m_impl;
+
+    XMLHttpRequestConstructor* m_xhr_constructor { nullptr };
+    XMLHttpRequestPrototype* m_xhr_prototype { nullptr };
 };
 
 }

Libraries/LibWeb/Bindings/XMLHttpRequestConstructor.cpp

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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 <LibJS/Heap/Heap.h>
+#include <LibJS/Interpreter.h>
+#include <LibWeb/Bindings/WindowObject.h>
+#include <LibWeb/Bindings/XMLHttpRequestConstructor.h>
+#include <LibWeb/Bindings/XMLHttpRequestWrapper.h>
+#include <LibWeb/DOM/XMLHttpRequest.h>
+
+namespace Web {
+namespace Bindings {
+
+XMLHttpRequestConstructor::XMLHttpRequestConstructor()
+{
+    put("length", JS::Value(1));
+}
+
+XMLHttpRequestConstructor::~XMLHttpRequestConstructor()
+{
+}
+
+JS::Value XMLHttpRequestConstructor::call(JS::Interpreter& interpreter)
+{
+    return construct(interpreter);
+}
+
+JS::Value XMLHttpRequestConstructor::construct(JS::Interpreter& interpreter)
+{
+    return interpreter.heap().allocate<XMLHttpRequestWrapper>(XMLHttpRequest::create());
+}
+
+}
+}

Libraries/LibWeb/Bindings/XMLHttpRequestConstructor.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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/NativeFunction.h>
+
+namespace Web {
+namespace Bindings {
+
+class XMLHttpRequestConstructor final : public JS::NativeFunction {
+public:
+    XMLHttpRequestConstructor();
+    virtual ~XMLHttpRequestConstructor() override;
+
+    virtual JS::Value call(JS::Interpreter&) override;
+    virtual JS::Value construct(JS::Interpreter&) override;
+
+private:
+    virtual bool has_constructor() const override { return true; }
+    virtual const char* class_name() const override { return "XMLHttpRequestConstructor"; }
+};
+
+}
+}

Libraries/LibWeb/Bindings/XMLHttpRequestPrototype.cpp

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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 <LibWeb/Bindings/XMLHttpRequestPrototype.h>
+#include <LibWeb/Bindings/XMLHttpRequestWrapper.h>
+#include <LibWeb/DOM/XMLHttpRequest.h>
+
+namespace Web {
+namespace Bindings {
+
+XMLHttpRequestPrototype::XMLHttpRequestPrototype()
+{
+    put_native_function("open", open, 2);
+    put_native_function("send", send, 0);
+    put_native_property("responseText", response_text_getter, nullptr);
+}
+
+XMLHttpRequestPrototype::~XMLHttpRequestPrototype()
+{
+}
+
+static XMLHttpRequest* impl_from(JS::Interpreter& interpreter)
+{
+    auto* this_object = interpreter.this_value().to_object(interpreter.heap());
+    if (!this_object)
+        return nullptr;
+    if (StringView("XMLHttpRequestWrapper") != this_object->class_name()) {
+        interpreter.throw_exception<JS::Error>("TypeError", "This is not an XMLHttpRequest object");
+        return nullptr;
+    }
+    return &static_cast<XMLHttpRequestWrapper*>(this_object)->impl();
+}
+
+JS::Value XMLHttpRequestPrototype::open(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    impl->open(interpreter.argument(0).to_string(), interpreter.argument(1).to_string());
+    return JS::js_undefined();
+}
+
+JS::Value XMLHttpRequestPrototype::send(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    impl->send();
+    return JS::js_undefined();
+}
+
+JS::Value XMLHttpRequestPrototype::response_text_getter(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    return JS::js_string(interpreter, impl->response_text());
+}
+
+}
+}

Libraries/LibWeb/Bindings/XMLHttpRequestPrototype.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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 Web {
+namespace Bindings {
+
+class XMLHttpRequestPrototype final : public JS::Object {
+public:
+    XMLHttpRequestPrototype();
+    virtual ~XMLHttpRequestPrototype() override;
+
+private:
+    virtual const char* class_name() const override { return "XMLHttpRequestPrototype"; }
+
+    static JS::Value open(JS::Interpreter&);
+    static JS::Value send(JS::Interpreter&);
+
+    static JS::Value response_text_getter(JS::Interpreter&);
+};
+
+}
+}

Libraries/LibWeb/Bindings/XMLHttpRequestWrapper.cpp

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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/FlyString.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Value.h>
+#include <LibWeb/Bindings/WindowObject.h>
+#include <LibWeb/Bindings/XMLHttpRequestPrototype.h>
+#include <LibWeb/Bindings/XMLHttpRequestWrapper.h>
+#include <LibWeb/DOM/XMLHttpRequest.h>
+
+namespace Web {
+namespace Bindings {
+
+XMLHttpRequestWrapper* wrap(JS::Heap& heap, XMLHttpRequest& impl)
+{
+    return static_cast<XMLHttpRequestWrapper*>(wrap_impl(heap, impl));
+}
+
+XMLHttpRequestWrapper::XMLHttpRequestWrapper(XMLHttpRequest& impl)
+    : EventTargetWrapper(impl)
+{
+    set_prototype(static_cast<WindowObject&>(interpreter().global_object()).xhr_prototype());
+}
+
+XMLHttpRequestWrapper::~XMLHttpRequestWrapper()
+{
+}
+
+XMLHttpRequest& XMLHttpRequestWrapper::impl()
+{
+    return static_cast<XMLHttpRequest&>(EventTargetWrapper::impl());
+}
+
+const XMLHttpRequest& XMLHttpRequestWrapper::impl() const
+{
+    return static_cast<const XMLHttpRequest&>(EventTargetWrapper::impl());
+}
+
+}
+}

Libraries/LibWeb/Bindings/XMLHttpRequestWrapper.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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 <LibWeb/Bindings/EventTargetWrapper.h>
+
+namespace Web {
+namespace Bindings {
+
+class XMLHttpRequestWrapper final : public EventTargetWrapper {
+public:
+    explicit XMLHttpRequestWrapper(XMLHttpRequest&);
+    virtual ~XMLHttpRequestWrapper() override;
+
+    XMLHttpRequest& impl();
+    const XMLHttpRequest& impl() const;
+
+private:
+    virtual const char* class_name() const override { return "XMLHttpRequestWrapper"; }
+};
+
+XMLHttpRequestWrapper* wrap(JS::Heap&, XMLHttpRequest&);
+
+}
+}

Libraries/LibWeb/DOM/XMLHttpRequest.cpp

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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 <LibJS/Interpreter.h>
+#include <LibJS/Runtime/Function.h>
+#include <LibWeb/Bindings/EventWrapper.h>
+#include <LibWeb/Bindings/XMLHttpRequestWrapper.h>
+#include <LibWeb/DOM/Event.h>
+#include <LibWeb/DOM/EventListener.h>
+#include <LibWeb/DOM/XMLHttpRequest.h>
+#include <LibWeb/ResourceLoader.h>
+
+namespace Web {
+
+XMLHttpRequest::XMLHttpRequest()
+{
+}
+
+XMLHttpRequest::~XMLHttpRequest()
+{
+}
+
+String XMLHttpRequest::response_text() const
+{
+    if (m_response.is_null())
+        return {};
+    return String::copy(m_response);
+}
+
+void XMLHttpRequest::open(const String& method, const String& url)
+{
+    m_method = method;
+    m_url = url;
+}
+
+void XMLHttpRequest::send()
+{
+    ResourceLoader::the().load(
+        URL(m_url),
+        [weak_this = make_weak_ptr()](auto& data) {
+            if (!weak_this)
+                return;
+            const_cast<XMLHttpRequest&>(*weak_this).m_response = data;
+            const_cast<XMLHttpRequest&>(*weak_this).dispatch_event(Event::create("load"));
+        },
+        [weak_this = make_weak_ptr()](auto& error) {
+            if (!weak_this)
+                return;
+            dbg() << "XHR failed to load: " << error;
+            const_cast<XMLHttpRequest&>(*weak_this).dispatch_event(Event::create("error"));
+        });
+}
+
+void XMLHttpRequest::dispatch_event(NonnullRefPtr<Event> event)
+{
+    for (auto& listener : listeners()) {
+        if (listener.event_name == event->name()) {
+            auto* function = const_cast<EventListener&>(*listener.listener).function();
+            auto* this_value = wrap(function->heap(), *this);
+            auto* event_wrapper = wrap(function->heap(), *event);
+            function->interpreter().call(function, this_value, { event_wrapper });
+        }
+    }
+}
+
+}

Libraries/LibWeb/DOM/XMLHttpRequest.h

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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 <AK/ByteBuffer.h>
+#include <AK/RefCounted.h>
+#include <AK/Weakable.h>
+#include <LibWeb/Bindings/Wrappable.h>
+#include <LibWeb/DOM/EventTarget.h>
+
+namespace Web {
+
+class XMLHttpRequest final
+    : public RefCounted<XMLHttpRequest>
+    , public Weakable<XMLHttpRequest>
+    , public EventTarget
+    , public Bindings::Wrappable {
+public:
+    using WrapperType = Bindings::XMLHttpRequestWrapper;
+
+    static NonnullRefPtr<XMLHttpRequest> create() { return adopt(*new XMLHttpRequest); }
+
+    virtual ~XMLHttpRequest() override;
+
+    using RefCounted::ref;
+    using RefCounted::unref;
+
+    String response_text() const;
+    void open(const String& method, const String& url);
+    void send();
+
+private:
+    virtual void ref_event_target() override { ref(); }
+    virtual void unref_event_target() override { unref(); }
+    virtual void dispatch_event(NonnullRefPtr<Event>) override;
+
+    XMLHttpRequest();
+
+    String m_method;
+    String m_url;
+
+    ByteBuffer m_response;
+};
+
+}

Libraries/LibWeb/Forward.h

@@ -51,6 +51,7 @@ class StyleResolver;
 class StyleRule;
 class StyleSheet;
 class Window;
+class XMLHttpRequest;
 
 namespace Bindings {
 
@@ -66,8 +67,10 @@ class NodeWrapper;
 class WindowObject;
 class Wrappable;
 class Wrapper;
+class XMLHttpRequestConstructor;
+class XMLHttpRequestPrototype;
+class XMLHttpRequestWrapper;
 
 }
 
-
 }

Libraries/LibWeb/Makefile

@@ -11,6 +11,9 @@ LIBWEB_OBJS = \
     Bindings/NodeWrapper.o \
     Bindings/WindowObject.o \
     Bindings/Wrappable.o \
+    Bindings/XMLHttpRequestConstructor.o \
+    Bindings/XMLHttpRequestPrototype.o \
+    Bindings/XMLHttpRequestWrapper.o \
     CSS/DefaultStyleSheetSource.o \
     CSS/PropertyID.o \
     CSS/Selector.o \
@@ -54,6 +57,7 @@ LIBWEB_OBJS = \
     DOM/ParentNode.o \
     DOM/Text.o \
     DOM/Window.o \
+    DOM/XMLHttpRequest.o \
     StylePropertiesModel.o \
     DOMTreeModel.o \
     Dump.o \