diff --git a/Meta/Lagom/CMakeLists.txt b/Meta/Lagom/CMakeLists.txt
index af7e4eb714..8b61fe063a 100644
--- a/Meta/Lagom/CMakeLists.txt
+++ b/Meta/Lagom/CMakeLists.txt
@@ -474,6 +474,15 @@ if (BUILD_LAGOM)
 
         add_executable(js ../../Userland/Utilities/js.cpp)
         target_link_libraries(js LibCrypto LibJS LibLine LibLocale LibMain LibTextCodec Threads::Threads)
+        if (EMSCRIPTEN)
+            add_executable(libjs Wasm/js_repl.cpp)
+            target_link_libraries(libjs LibJS)
+            target_link_options(libjs PRIVATE
+                    -sEXPORTED_FUNCTIONS=_initialize_repl,_execute
+                    -sEXPORTED_RUNTIME_METHODS=allocateUTF8
+                    -sERROR_ON_UNDEFINED_SYMBOLS=0
+                    -sENVIRONMENT=web)
+        endif()
 
         add_executable(markdown-check ../../Userland/Utilities/markdown-check.cpp)
         target_link_libraries(markdown-check LibMarkdown LibMain)
diff --git a/Meta/Lagom/Wasm/js_repl.cpp b/Meta/Lagom/Wasm/js_repl.cpp
new file mode 100644
index 0000000000..76674d3af0
--- /dev/null
+++ b/Meta/Lagom/Wasm/js_repl.cpp
@@ -0,0 +1,388 @@
+/*
+ * Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2020-2022, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2020-2022, Ali Mohammad Pur <mpfard@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/ArgsParser.h>
+#include <LibCore/ConfigFile.h>
+#include <LibCore/StandardPaths.h>
+#include <LibCore/Stream.h>
+#include <LibCore/System.h>
+#include <LibJS/AST.h>
+#include <LibJS/Bytecode/BasicBlock.h>
+#include <LibJS/Bytecode/Generator.h>
+#include <LibJS/Bytecode/Interpreter.h>
+#include <LibJS/Console.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Parser.h>
+#include <LibJS/Print.h>
+#include <LibJS/Runtime/ConsoleObject.h>
+#include <LibJS/Runtime/JSONObject.h>
+#include <LibJS/Runtime/StringPrototype.h>
+#include <LibJS/SourceTextModule.h>
+#include <LibLine/Editor.h>
+#include <LibMain/Main.h>
+#include <LibTextCodec/Decoder.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#ifndef AK_OS_EMSCRIPTEN
+#    error "This program is for Emscripten only"
+#endif
+
+#include <emscripten.h>
+
+class ReplConsoleClient;
+
+RefPtr<JS::VM> g_vm;
+OwnPtr<JS::Interpreter> g_interpreter;
+OwnPtr<ReplConsoleClient> g_console_client;
+JS::Handle<JS::Value> g_last_value = JS::make_handle(JS::js_undefined());
+
+EM_JS(void, user_display, (char const* string, u32 length), { globalDisplayToUser(UTF8ToString(string, length)); });
+
+template<typename... Args>
+void display(CheckedFormatString<Args...> format_string, Args const&... args)
+{
+    auto string = String::formatted(format_string.view(), args...);
+    user_display(string.characters(), string.length());
+}
+
+template<typename... Args>
+void displayln(CheckedFormatString<Args...> format_string, Args const&... args)
+{
+    display(format_string.view(), args...);
+    user_display("\n", 1);
+}
+
+void displayln() { user_display("\n", 1); }
+
+class UserDisplayStream final : public Core::Stream::Stream {
+    virtual ErrorOr<Bytes> read(Bytes) override { return Error::from_string_view("Not readable"sv); };
+    virtual bool is_writable() const override { return true; }
+    virtual ErrorOr<size_t> write(ReadonlyBytes bytes) override
+    {
+        user_display(bit_cast<char const*>(bytes.data()), bytes.size());
+        return bytes.size();
+    }
+    virtual bool is_eof() const override { return true; }
+    virtual bool is_open() const override { return true; }
+    virtual void close() override { }
+};
+
+ErrorOr<void> print(JS::Value value)
+{
+    UserDisplayStream stream;
+    JS::PrintContext print_context {
+        .vm = *g_vm,
+        .stream = stream,
+        .strip_ansi = true,
+    };
+    return JS::print(value, print_context);
+}
+
+class ReplObject final : public JS::GlobalObject {
+    JS_OBJECT(ReplObject, JS::GlobalObject);
+
+public:
+    ReplObject(JS::Realm& realm)
+        : GlobalObject(realm)
+    {
+    }
+    virtual void initialize(JS::Realm&) override;
+    virtual ~ReplObject() override = default;
+
+private:
+    JS_DECLARE_NATIVE_FUNCTION(last_value_getter);
+    JS_DECLARE_NATIVE_FUNCTION(print);
+};
+
+static bool s_dump_ast = false;
+static bool s_run_bytecode = false;
+static bool s_opt_bytecode = false;
+static bool s_as_module = false;
+static bool s_print_last_result = false;
+
+static bool parse_and_run(JS::Interpreter& interpreter, StringView source, StringView source_name)
+{
+    enum class ReturnEarly {
+        No,
+        Yes,
+    };
+
+    JS::ThrowCompletionOr<JS::Value> result { JS::js_undefined() };
+
+    auto run_script_or_module = [&](auto& script_or_module) {
+        if (s_dump_ast)
+            script_or_module->parse_node().dump(0);
+
+        if (JS::Bytecode::g_dump_bytecode || s_run_bytecode) {
+            auto executable_result = JS::Bytecode::Generator::generate(script_or_module->parse_node());
+            if (executable_result.is_error()) {
+                result = g_vm->throw_completion<JS::InternalError>(executable_result.error().to_string());
+                return ReturnEarly::No;
+            }
+
+            auto executable = executable_result.release_value();
+            executable->name = source_name;
+            if (s_opt_bytecode) {
+                auto& passes = JS::Bytecode::Interpreter::optimization_pipeline();
+                passes.perform(*executable);
+            }
+
+            if (JS::Bytecode::g_dump_bytecode)
+                executable->dump();
+
+            if (s_run_bytecode) {
+                JS::Bytecode::Interpreter bytecode_interpreter(interpreter.realm());
+                auto result_or_error = bytecode_interpreter.run_and_return_frame(*executable, nullptr);
+                if (result_or_error.value.is_error())
+                    result = result_or_error.value.release_error();
+                else
+                    result = result_or_error.frame->registers[0];
+            } else {
+                return ReturnEarly::Yes;
+            }
+        } else {
+            result = interpreter.run(*script_or_module);
+        }
+
+        return ReturnEarly::No;
+    };
+
+    if (!s_as_module) {
+        auto script_or_error = JS::Script::parse(source, interpreter.realm(), source_name);
+        if (script_or_error.is_error()) {
+            auto error = script_or_error.error()[0];
+            auto hint = error.source_location_hint(source);
+            if (!hint.is_empty())
+                displayln("{}", hint);
+            displayln("{}", error.to_string());
+            result = interpreter.vm().throw_completion<JS::SyntaxError>(error.to_string());
+        } else {
+            auto return_early = run_script_or_module(script_or_error.value());
+            if (return_early == ReturnEarly::Yes)
+                return true;
+        }
+    } else {
+        auto module_or_error = JS::SourceTextModule::parse(source, interpreter.realm(), source_name);
+        if (module_or_error.is_error()) {
+            auto error = module_or_error.error()[0];
+            auto hint = error.source_location_hint(source);
+            if (!hint.is_empty())
+                displayln("{}", hint);
+            displayln(error.to_string());
+            result = interpreter.vm().throw_completion<JS::SyntaxError>(error.to_string());
+        } else {
+            auto return_early = run_script_or_module(module_or_error.value());
+            if (return_early == ReturnEarly::Yes)
+                return true;
+        }
+    }
+
+    auto handle_exception = [&](JS::Value thrown_value) {
+        display("Uncaught exception: ");
+        (void)print(thrown_value);
+
+        if (!thrown_value.is_object() || !is<JS::Error>(thrown_value.as_object()))
+            return;
+        auto& traceback = static_cast<JS::Error const&>(thrown_value.as_object()).traceback();
+        if (traceback.size() > 1) {
+            unsigned repetitions = 0;
+            for (size_t i = 0; i < traceback.size(); ++i) {
+                auto& traceback_frame = traceback[i];
+                if (i + 1 < traceback.size()) {
+                    auto& next_traceback_frame = traceback[i + 1];
+                    if (next_traceback_frame.function_name == traceback_frame.function_name) {
+                        repetitions++;
+                        continue;
+                    }
+                }
+                if (repetitions > 4) {
+                    // If more than 5 (1 + >4) consecutive function calls with the same name, print
+                    // the name only once and show the number of repetitions instead. This prevents
+                    // printing ridiculously large call stacks of recursive functions.
+                    displayln(" -> {}", traceback_frame.function_name);
+                    displayln(" {} more calls", repetitions);
+                } else {
+                    for (size_t j = 0; j < repetitions + 1; ++j)
+                        displayln(" -> {}", traceback_frame.function_name);
+                }
+                repetitions = 0;
+            }
+        }
+    };
+
+    if (!result.is_error())
+        g_last_value = JS::make_handle(result.value());
+
+    if (result.is_error()) {
+        VERIFY(result.throw_completion().value().has_value());
+        handle_exception(*result.release_error().value());
+        return false;
+    }
+
+    if (s_print_last_result) {
+        (void)print(result.value());
+        display("\n");
+    }
+
+    return true;
+}
+
+void ReplObject::initialize(JS::Realm& realm)
+{
+    Base::initialize(realm);
+
+    define_direct_property("global", this, JS::Attribute::Enumerable);
+    u8 attr = JS::Attribute::Configurable | JS::Attribute::Writable | JS::Attribute::Enumerable;
+    define_native_function(realm, "print", print, 1, attr);
+
+    define_native_accessor(
+        realm,
+        "_",
+        [](JS::VM&) {
+            return g_last_value.value();
+        },
+        [](JS::VM& vm) -> JS::ThrowCompletionOr<JS::Value> {
+            auto& global_object = vm.get_global_object();
+            VERIFY(is<ReplObject>(global_object));
+            displayln("Disable writing last value to '_'");
+
+            // We must delete first otherwise this setter gets called recursively.
+            TRY(global_object.internal_delete(JS::PropertyKey { "_" }));
+
+            auto value = vm.argument(0);
+            TRY(global_object.internal_set(JS::PropertyKey { "_" }, value, &global_object));
+            return value;
+        },
+        attr);
+}
+
+JS_DEFINE_NATIVE_FUNCTION(ReplObject::print)
+{
+    auto result = ::print(vm.argument(0));
+    if (result.is_error())
+        return g_vm->throw_completion<JS::InternalError>(String::formatted("Failed to print value: {}", result.error()));
+
+    displayln();
+
+    return JS::js_undefined();
+}
+
+class ReplConsoleClient final : public JS::ConsoleClient {
+public:
+    ReplConsoleClient(JS::Console& console)
+        : ConsoleClient(console)
+    {
+    }
+
+    virtual void clear() override
+    {
+        display("FIXME: clear");
+        m_group_stack_depth = 0;
+    }
+
+    virtual void end_group() override
+    {
+        if (m_group_stack_depth > 0)
+            m_group_stack_depth--;
+    }
+
+    // 2.3. Printer(logLevel, args[, options]), https://console.spec.whatwg.org/#printer
+    virtual JS::ThrowCompletionOr<JS::Value> printer(JS::Console::LogLevel log_level, PrinterArguments arguments) override
+    {
+        String indent = String::repeated("  "sv, m_group_stack_depth);
+
+        if (log_level == JS::Console::LogLevel::Trace) {
+            auto trace = arguments.get<JS::Console::Trace>();
+            StringBuilder builder;
+            if (!trace.label.is_empty())
+                builder.appendff("{}{}\n", indent, trace.label);
+
+            for (auto& function_name : trace.stack)
+                builder.appendff("{}-> {}\n", indent, function_name);
+
+            displayln("{}", builder.string_view());
+            return JS::js_undefined();
+        }
+
+        if (log_level == JS::Console::LogLevel::Group || log_level == JS::Console::LogLevel::GroupCollapsed) {
+            auto group = arguments.get<JS::Console::Group>();
+            displayln("{}{}", indent, group.label);
+            m_group_stack_depth++;
+            return JS::js_undefined();
+        }
+
+        auto output = String::join(' ', arguments.get<JS::MarkedVector<JS::Value>>());
+        switch (log_level) {
+        case JS::Console::LogLevel::Debug:
+            displayln("{}{}", indent, output);
+            break;
+        case JS::Console::LogLevel::Error:
+        case JS::Console::LogLevel::Assert:
+            displayln("{}{}", indent, output);
+            break;
+        case JS::Console::LogLevel::Info:
+            displayln("{}(i) {}", indent, output);
+            break;
+        case JS::Console::LogLevel::Log:
+            displayln("{}{}", indent, output);
+            break;
+        case JS::Console::LogLevel::Warn:
+        case JS::Console::LogLevel::CountReset:
+            displayln("{}{}", indent, output);
+            break;
+        default:
+            displayln("{}{}", indent, output);
+            break;
+        }
+        return JS::js_undefined();
+    }
+
+private:
+    int m_group_stack_depth { 0 };
+};
+
+extern "C" int initialize_repl()
+{
+    g_vm = JS::VM::create();
+    g_vm->enable_default_host_import_module_dynamically_hook();
+
+    // NOTE: These will print out both warnings when using something like Promise.reject().catch(...) -
+    // which is, as far as I can tell, correct - a promise is created, rejected without handler, and a
+    // handler then attached to it. The Node.js REPL doesn't warn in this case, so it's something we
+    // might want to revisit at a later point and disable warnings for promises created this way.
+    g_vm->on_promise_unhandled_rejection = [](auto& promise) {
+        display("WARNING: A promise was rejected without any handlers");
+        display(" (result: ");
+        (void)print(promise.result());
+        displayln(")");
+    };
+    g_vm->on_promise_rejection_handled = [](auto& promise) {
+        display("WARNING: A handler was added to an already rejected promise");
+        display(" (result: ");
+        (void)print(promise.result());
+        displayln(")");
+    };
+    OwnPtr<JS::Interpreter> interpreter;
+
+    s_print_last_result = true;
+    interpreter = JS::Interpreter::create<ReplObject>(*g_vm);
+    auto& console_object = *interpreter->realm().intrinsics().console_object();
+    g_console_client = make<ReplConsoleClient>(console_object.console());
+    console_object.console().set_client(*g_console_client);
+    g_interpreter = move(interpreter);
+
+    return 0;
+}
+
+extern "C" bool execute(char const* s, u32 length)
+{
+    return parse_and_run(*g_interpreter, { s, length }, "REPL"sv);
+}