diff --git a/test/j2s/j2s.cc b/test/j2s/j2s.cc
new file mode 100644
index 000000000..8fba415e5
--- /dev/null
+++ b/test/j2s/j2s.cc
@@ -0,0 +1,36 @@
+#include "j2s.h"     // generated by:  gen j2s.proto
+#include "co/flag.h"
+#include "co/cout.h"
+
+int main(int argc, char** argv) {
+    flag::parse(argc, argv);
+
+    co::Json v;
+    v.add_member("b", false)
+     .add_member("i", 23)
+     .add_member("s", "hello")
+     .add_member("data", co::Json().add_member("ii", 11).add_member("ss", "good"))
+     .add_member("ai", co::Json().push_back(1).push_back(2).push_back(3))
+     .add_member("ao", co::Json().push_back(co::Json().add_member("xx", 88).add_member("yy", "nice")));
+
+    co::print("Json v:\n", v, '\n');
+    
+    xx::XX x;
+    x.from_json(v);
+
+    co::print("x.b: ", x.b);
+    co::print("x.i: ", x.i);
+    co::print("x.s: ", x.s);
+    co::print("x.data.ii: ", x.data.ii);
+    co::print("x.data.ss: ", x.data.ss);
+    co::print("x.ai[0]: ", x.ai[0]);
+    co::print("x.ai[1]: ", x.ai[1]);
+    co::print("x.ai[2]: ", x.ai[2]);
+    co::print("x.ao[0].xx: ", x.ao[0].xx);
+    co::print("x.ao[0].yy: ", x.ao[0].yy);
+
+    co::print("\nx.as_json():");
+    co::print(x.as_json());
+
+    return 0;
+}
diff --git a/test/j2s/j2s.h b/test/j2s/j2s.h
new file mode 100644
index 000000000..28e51a854
--- /dev/null
+++ b/test/j2s/j2s.h
@@ -0,0 +1,96 @@
+// Autogenerated.
+// DO NOT EDIT. All changes will be undone.
+#pragma once
+
+#include "co/json.h"
+
+namespace xx {
+
+struct XX {
+    struct _unamed_s1 {
+        int ii;
+        fastring ss;
+
+        void from_json(const co::Json& _x_) {
+            ii = (int)_x_.get("ii").as_int64();
+            ss = _x_.get("ss").as_c_str();
+        }
+
+        co::Json as_json() const {
+            co::Json _x_;
+            _x_.add_member("ii", ii);
+            _x_.add_member("ss", ss);
+            return _x_;
+        }
+    };
+
+    struct _unamed_s2 {
+        int xx;
+        fastring yy;
+
+        void from_json(const co::Json& _x_) {
+            xx = (int)_x_.get("xx").as_int64();
+            yy = _x_.get("yy").as_c_str();
+        }
+
+        co::Json as_json() const {
+            co::Json _x_;
+            _x_.add_member("xx", xx);
+            _x_.add_member("yy", yy);
+            return _x_;
+        }
+    };
+
+    bool b;
+    int i;
+    fastring s;
+    _unamed_s1 data;
+    co::vector<int> ai;
+    co::vector<_unamed_s2> ao;
+
+    void from_json(const co::Json& _x_) {
+        b = _x_.get("b").as_bool();
+        i = (int)_x_.get("i").as_int64();
+        s = _x_.get("s").as_c_str();
+        data.from_json(_x_.get("data"));
+        do {
+            auto& _unamed_v1 = _x_.get("ai");
+            for (uint32 i = 0; i < _unamed_v1.array_size(); ++i) {
+                ai.push_back((int)_unamed_v1[i].as_int64());
+            }
+        } while (0);
+        do {
+            auto& _unamed_v1 = _x_.get("ao");
+            for (uint32 i = 0; i < _unamed_v1.array_size(); ++i) {
+                _unamed_s2 _unamed_v2;
+                _unamed_v2.from_json(_unamed_v1[i]);
+                ao.emplace_back(std::move(_unamed_v2));
+            }
+        } while (0);
+    }
+
+    co::Json as_json() const {
+        co::Json _x_;
+        _x_.add_member("b", b);
+        _x_.add_member("i", i);
+        _x_.add_member("s", s);
+        _x_.add_member("data", data.as_json());
+        do {
+            co::Json _unamed_v1;
+            for (size_t i = 0; i < ai.size(); ++i) {
+                _unamed_v1.push_back(ai[i]);
+            }
+            _x_.add_member("ai", _unamed_v1);
+        } while (0);
+        do {
+            co::Json _unamed_v1;
+            for (size_t i = 0; i < ao.size(); ++i) {
+                _unamed_v1.push_back(ao[i].as_json());
+            }
+            _x_.add_member("ao", _unamed_v1);
+        } while (0);
+        return _x_;
+    }
+};
+
+} // xx
diff --git a/test/j2s/j2s.proto b/test/j2s/j2s.proto
new file mode 100644
index 000000000..90beea199
--- /dev/null
+++ b/test/j2s/j2s.proto
@@ -0,0 +1,16 @@
+package xx
+
+object XX {
+    bool b
+    int i
+    string s
+    data {       // anonymous object, field name can be put ahead
+        int ii
+        string ss
+    }
+    [int] ai     // array of int
+    ao [{        // array of anonymous object, field name can be put ahead
+        int xx
+        string yy
+    }]
+}