diff --git a/javascript-engine/src/engine.rs b/javascript-engine/src/engine.rs
index 187101b..3bb9f9c 100644
--- a/javascript-engine/src/engine.rs
+++ b/javascript-engine/src/engine.rs
@@ -1,16 +1,35 @@
 use boa_engine::{Context, JsValue};
 use boa_engine::property::Attribute;
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
 
+#[derive(Debug, Serialize, Deserialize)]
 pub(crate) struct EvalResult {
-    data: Option<JsValue>,
+    data: Option<Value>,
     error: Option<String>,
 }
 
 impl EvalResult {
     fn ok(data: JsValue) -> Self {
-        Self {
-            data: Some(data),
-            error: None,
+        match data {
+            JsValue::Undefined => {
+                return Self {
+                    data: None,
+                    error: None,
+                };
+            }
+            _ => {}
+        }
+        let mut context = Context::default();
+        match data.to_json(&mut context) {
+            Err(e) => Self {
+                data: None,
+                error: Some(format!("{}", e)),
+            },
+            Ok(data_json) => Self {
+                data: Some(data_json),
+                error: None,
+            }
         }
     }
     fn err(error: String) -> Self {
diff --git a/javascript-engine/src/lib.rs b/javascript-engine/src/lib.rs
index a616e01..b6cc094 100644
--- a/javascript-engine/src/lib.rs
+++ b/javascript-engine/src/lib.rs
@@ -1,11 +1,11 @@
-
 mod mem;
 mod engine;
 
-
 #[no_mangle]
-pub unsafe fn eval(ptr: *mut u8, len: usize) -> *mut u8 {
-    // let eval_result = engine::inner_eval()
-    unimplemented!()
+pub unsafe fn eval(ptr: *mut u8, len: usize) -> (*mut u8, usize) {
+    let js = mem::read_string(ptr, len);
+    let eval_result = engine::inner_eval(&js);
+    let eval_result_json_string = serde_json::to_string(&eval_result).expect("SHOULD NOT HAPPEN");
+    mem::malloc_and_write_string(&eval_result_json_string)
 }