diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..3388018
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "ext/quickjsrb/quickjs"]
+	path = ext/quickjsrb/quickjs
+	url = https://github.com/bellard/quickjs.git
diff --git a/ext/quickjsrb/extconf.rb b/ext/quickjsrb/extconf.rb
index 0602c9c..da49070 100644
--- a/ext/quickjsrb/extconf.rb
+++ b/ext/quickjsrb/extconf.rb
@@ -2,9 +2,44 @@
 
 require 'mkmf'
 
+$VPATH << "$(srcdir)/quickjs"
+
+$srcs = [
+  'libunicode.c',
+  'libbf.c',
+  'libregexp.c',
+  'cutils.c',
+  'quickjs.c',
+  'quickjs-libc.c',
+  'quickjsrb.c',
+]
+
+append_cflags('-I$(srcdir)/quickjs')
+
+append_cflags('-fwrapv')
+append_cflags('-g')
+append_cflags('-O2')
+append_cflags('-Wall')
+append_cflags('-MMD')
+append_cflags('-MF')
+append_cflags('-Wextra')
+append_cflags('-Wno-sign-compare')
+append_cflags('-Wno-missing-field-initializers')
+append_cflags('-Wundef -Wuninitialized')
+append_cflags('-Wunused -Wno-unused-parameter')
+append_cflags('-Wwrite-strings')
+append_cflags('-Wchar-subscripts -funsigned-char')
+append_cflags('-D_GNU_SOURCE -DCONFIG_VERSION=\"2024-02-14\" -DCONFIG_BIGNUM')
+
+abort('could not find quickjs.h') unless find_header('quickjs.h')
+abort('could not find cutils.h') unless find_header('cutils.h')
+abort('could not find quickjs-libc.h') unless find_header('quickjs-libc.h')
+#abort('could not find libbf.h') unless find_header('libbf.h')
+
 # Makes all symbols private by default to avoid unintended conflict
 # with other gems. To explicitly export symbols you can use RUBY_FUNC_EXPORTED
 # selectively, or entirely remove this flag.
 append_cflags('-fvisibility=hidden')
+$warnflags = ''
 
 create_makefile('quickjsrb/quickjsrb')
diff --git a/ext/quickjsrb/quickjs b/ext/quickjsrb/quickjs
new file mode 160000
index 0000000..36911f0
--- /dev/null
+++ b/ext/quickjsrb/quickjs
@@ -0,0 +1 @@
+Subproject commit 36911f0d3ab1a4c190a4d5cbe7c2db225a455389
diff --git a/ext/quickjsrb/quickjsrb.c b/ext/quickjsrb/quickjsrb.c
index 56ca9a1..675fb4f 100644
--- a/ext/quickjsrb/quickjsrb.c
+++ b/ext/quickjsrb/quickjsrb.c
@@ -2,16 +2,42 @@
 
 VALUE rb_mQuickjs;
 
-
-VALUE rb_module_say_hi(VALUE klass)
+VALUE rb_module_eval_js_code(VALUE klass, VALUE r_code)
 {
-    VALUE r_hello = rb_str_new2("Hello!");
-    return r_hello;
+  JSRuntime *rt = JS_NewRuntime();
+  JSContext *ctx = JS_NewContext(rt);
+
+  JS_SetMemoryLimit(rt, 0x4000000);
+  JS_SetMaxStackSize(rt, 0x10000);
+  JS_AddIntrinsicBigFloat(ctx);
+  JS_AddIntrinsicBigDecimal(ctx);
+  JS_AddIntrinsicOperators(ctx);
+  JS_EnableBignumExt(ctx, 1);
+  JS_SetModuleLoaderFunc(rt, NULL, js_module_loader, NULL);
+  js_std_add_helpers(ctx, 0, NULL);
+
+  js_std_init_handlers(rt);
+  js_init_module_std(ctx, "std");
+  js_init_module_os(ctx, "os");
+
+  char *code = StringValueCStr(r_code);
+  JSValue res = JS_Eval(ctx, code, strlen(code), "<code>", JS_EVAL_TYPE_GLOBAL);
+
+  int r = 0;
+  if (JS_IsException(res)) {
+  } else {
+    JS_ToInt32(ctx, &r, res);
+  }
+  JS_FreeValue(ctx, res);
+  JS_FreeContext(ctx);
+  JS_FreeRuntime(rt);
+
+  return INT2NUM(r);
 }
 
 RUBY_FUNC_EXPORTED void
 Init_quickjsrb(void)
 {
   rb_mQuickjs = rb_define_module("Quickjs");
-  rb_define_module_function(rb_mQuickjs, "say_hi", rb_module_say_hi, 0);
+  rb_define_module_function(rb_mQuickjs, "evalCode", rb_module_eval_js_code, 1);
 }
diff --git a/ext/quickjsrb/quickjsrb.h b/ext/quickjsrb/quickjsrb.h
index 95d32c7..860b820 100644
--- a/ext/quickjsrb/quickjsrb.h
+++ b/ext/quickjsrb/quickjsrb.h
@@ -1,6 +1,14 @@
-#ifndef QUICKJS_H
-#define QUICKJS_H 1
+#ifndef QUICKJSRB_H
+#define QUICKJSRB_H 1
 
 #include "ruby.h"
 
-#endif /* QUICKJS_H */
+#include "quickjs.h"
+#include "quickjs-libc.h"
+
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+
+#endif /* QUICKJSRB_H */
diff --git a/test/quickjs_test.rb b/test/quickjs_test.rb
index 4f939a6..dd9e974 100644
--- a/test/quickjs_test.rb
+++ b/test/quickjs_test.rb
@@ -9,7 +9,8 @@ class QuickjsTest < Test::Unit::TestCase
     end
   end
 
-  test "something useful" do
-    assert_equal(::Quickjs.say_hi, "Hello!")
+  test "support returning integer" do
+    assert_equal(::Quickjs.evalCode("2+3"), 5)
+    assert_equal(::Quickjs.evalCode("const func = () => 8; func();"), 8)
   end
 end