diff --git a/Cargo.lock b/Cargo.lock
index a2f81726..a03f91b5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -788,6 +788,7 @@ dependencies = [
  "ring",
  "rle",
  "serde",
+ "serde-wasm-bindgen",
  "serde_columnar",
  "serde_json",
  "smallvec",
@@ -1483,6 +1484,17 @@ dependencies = [
  "serde_derive",
 ]
 
+[[package]]
+name = "serde-wasm-bindgen"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3b4c031cd0d9014307d82b8abf653c0290fbdaeb4c02d00c63cf52f728628bf"
+dependencies = [
+ "js-sys",
+ "serde",
+ "wasm-bindgen",
+]
+
 [[package]]
 name = "serde_columnar"
 version = "0.1.0"
diff --git a/crates/loro-core/Cargo.toml b/crates/loro-core/Cargo.toml
index 4935674d..e469f342 100644
--- a/crates/loro-core/Cargo.toml
+++ b/crates/loro-core/Cargo.toml
@@ -26,6 +26,7 @@ tabled = { version = "0.10.0", optional = true }
 colored = "2.0.0"
 bit-vec = "0.6.3"
 wasm-bindgen = { version = "0.2.83", optional = true }
+serde-wasm-bindgen = { version = "0.4.5", optional = true }
 js-sys = { version = "0.3.60", optional = true }
 serde_json = { version = "1.0.87", optional = true }
 arref = "0.1.0"
@@ -52,7 +53,7 @@ debug-log = "0.1.1"
 doctest = false
 
 [features]
-wasm = ["wasm-bindgen", "js-sys"]
+wasm = ["wasm-bindgen", "js-sys", "serde-wasm-bindgen"]
 json = ["serde_json"]
 # whether to use list slice instead of raw str in text container
 test_utils = ["crdt-list/fuzzing", "rand", "arbitrary", "tabled", "json"]
diff --git a/crates/loro-core/src/container/list/list_container.rs b/crates/loro-core/src/container/list/list_container.rs
index 55c82ae1..9a6485f9 100644
--- a/crates/loro-core/src/container/list/list_container.rs
+++ b/crates/loro-core/src/container/list/list_container.rs
@@ -23,6 +23,7 @@ use crate::{
     op::{InnerContent, Op, RemoteContent, RichOp},
     value::LoroValue,
     version::IdSpanVector,
+    LoroError,
 };
 
 use super::list_op::InnerListOp;
@@ -90,6 +91,13 @@ impl ListContainer {
         Some(id)
     }
 
+    pub fn get(&self, pos: usize) -> Option<LoroValue> {
+        self.state
+            .get(pos)
+            .map(|range| self.raw_data.slice(&range.as_ref().0))
+            .and_then(|slice| slice.first().cloned())
+    }
+
     pub fn delete<C: Context>(&mut self, ctx: &C, pos: usize, len: usize) -> Option<ID> {
         if len == 0 {
             return None;
@@ -279,7 +287,12 @@ impl List {
         }
     }
 
-    pub fn insert_batch<C: Context>(&mut self, ctx: &C, pos: usize, values: Vec<LoroValue>) {
+    pub fn insert_batch<C: Context>(
+        &mut self,
+        ctx: &C,
+        pos: usize,
+        values: Vec<LoroValue>,
+    ) -> Result<(), LoroError> {
         self.with_container_checked(ctx, |x| x.insert_batch(ctx, pos, values))
     }
 
@@ -288,7 +301,7 @@ impl List {
         ctx: &C,
         pos: usize,
         value: V,
-    ) -> Option<ID> {
+    ) -> Result<Option<ID>, LoroError> {
         self.with_container_checked(ctx, |x| x.insert(ctx, pos, value))
     }
 
@@ -297,12 +310,21 @@ impl List {
         ctx: &C,
         pos: usize,
         obj: ContainerType,
-    ) -> ContainerID {
+    ) -> Result<ContainerID, LoroError> {
         self.with_container_checked(ctx, |x| x.insert_obj(ctx, pos, obj))
     }
 
-    pub fn delete<C: Context>(&mut self, ctx: &C, pos: usize, len: usize) -> Option<ID> {
-        self.with_container_checked(ctx, |text| text.delete(ctx, pos, len))
+    pub fn delete<C: Context>(
+        &mut self,
+        ctx: &C,
+        pos: usize,
+        len: usize,
+    ) -> Result<Option<ID>, LoroError> {
+        self.with_container_checked(ctx, |list| list.delete(ctx, pos, len))
+    }
+
+    pub fn get(&self, pos: usize) -> Option<LoroValue> {
+        self.with_container(|list| list.get(pos))
     }
 
     pub fn len(&self) -> usize {
diff --git a/crates/loro-core/src/container/map/map_container.rs b/crates/loro-core/src/container/map/map_container.rs
index 1420ed0f..6b60d1b5 100644
--- a/crates/loro-core/src/container/map/map_container.rs
+++ b/crates/loro-core/src/container/map/map_container.rs
@@ -117,6 +117,11 @@ impl MapContainer {
     pub fn delete<C: Context>(&mut self, ctx: &C, key: InternalString) {
         self.insert(ctx, key, LoroValue::Null);
     }
+
+    #[inline]
+    pub fn get(&self, key: &InternalString) -> Option<LoroValue> {
+        self.state.get(key).map(|v| &v.value).cloned()
+    }
 }
 
 impl Container for MapContainer {
@@ -230,7 +235,12 @@ impl Map {
         }
     }
 
-    pub fn insert<C: Context, V: Into<LoroValue>>(&mut self, ctx: &C, key: &str, value: V) {
+    pub fn insert<C: Context, V: Into<LoroValue>>(
+        &mut self,
+        ctx: &C,
+        key: &str,
+        value: V,
+    ) -> Result<(), crate::LoroError> {
         self.with_container_checked(ctx, |map| {
             map.insert(ctx, key.into(), value);
         })
@@ -241,16 +251,20 @@ impl Map {
         ctx: &C,
         key: &str,
         obj: ContainerType,
-    ) -> ContainerID {
+    ) -> Result<ContainerID, crate::LoroError> {
         self.with_container_checked(ctx, |map| map.insert_obj(ctx, key.into(), obj))
     }
 
-    pub fn delete<C: Context>(&mut self, ctx: &C, key: &str) {
+    pub fn delete<C: Context>(&mut self, ctx: &C, key: &str) -> Result<(), crate::LoroError> {
         self.with_container_checked(ctx, |map| {
             map.delete(ctx, key.into());
         })
     }
 
+    pub fn get(&self, key: &str) -> Option<LoroValue> {
+        self.with_container(|map| map.get(&key.into()))
+    }
+
     pub fn id(&self) -> ContainerID {
         self.instance.lock().unwrap().as_map().unwrap().id.clone()
     }
diff --git a/crates/loro-core/src/container/registry.rs b/crates/loro-core/src/container/registry.rs
index a81e0d78..16bd8033 100644
--- a/crates/loro-core/src/container/registry.rs
+++ b/crates/loro-core/src/container/registry.rs
@@ -14,7 +14,7 @@ use crate::{
     id::{ClientID, ContainerIdx},
     op::{RemoteContent, RichOp},
     version::IdSpanVector,
-    LoroValue, VersionVector,
+    LoroError, LoroValue, VersionVector,
 };
 
 use super::{
@@ -297,19 +297,18 @@ pub trait ContainerWrapper {
     where
         F: FnOnce(&mut Self::Container) -> R;
 
-    fn with_container_checked<C: Context, F, R>(&self, ctx: &C, f: F) -> R
+    fn with_container_checked<C: Context, F, R>(&self, ctx: &C, f: F) -> Result<R, LoroError>
     where
         F: FnOnce(&mut Self::Container) -> R,
     {
         let store_client_id = ctx.log_store().read().unwrap().this_client_id();
         if store_client_id != self.client_id() {
-            panic!(
-                "Context's client_id({}) does not match Container's client_id({})",
-                store_client_id,
-                self.client_id()
-            );
+            return Err(LoroError::UnmatchedContext {
+                expected: self.client_id(),
+                found: store_client_id,
+            });
         }
-        self.with_container(f)
+        Ok(self.with_container(f))
     }
 
     fn client_id(&self) -> ClientID;
diff --git a/crates/loro-core/src/container/text/text_container.rs b/crates/loro-core/src/container/text/text_container.rs
index bab010d9..0467c9af 100644
--- a/crates/loro-core/src/container/text/text_container.rs
+++ b/crates/loro-core/src/container/text/text_container.rs
@@ -302,11 +302,21 @@ impl Text {
         self.instance.lock().unwrap().as_text().unwrap().id.clone()
     }
 
-    pub fn insert<C: Context>(&mut self, ctx: &C, pos: usize, text: &str) -> Option<ID> {
+    pub fn insert<C: Context>(
+        &mut self,
+        ctx: &C,
+        pos: usize,
+        text: &str,
+    ) -> Result<Option<ID>, crate::LoroError> {
         self.with_container_checked(ctx, |x| x.insert(ctx, pos, text))
     }
 
-    pub fn delete<C: Context>(&mut self, ctx: &C, pos: usize, len: usize) -> Option<ID> {
+    pub fn delete<C: Context>(
+        &mut self,
+        ctx: &C,
+        pos: usize,
+        len: usize,
+    ) -> Result<Option<ID>, crate::LoroError> {
         self.with_container_checked(ctx, |text| text.delete(ctx, pos, len))
     }
 
diff --git a/crates/loro-core/src/error.rs b/crates/loro-core/src/error.rs
index c0d81e1e..8554b8d7 100644
--- a/crates/loro-core/src/error.rs
+++ b/crates/loro-core/src/error.rs
@@ -1,7 +1,11 @@
 use thiserror::Error;
 
+use crate::id::ClientID;
+
 #[derive(Error, Debug)]
 pub enum LoroError {
+    #[error("Context's client_id({found:?}) does not match Container's client_id({expected:?})")]
+    UnmatchedContext { expected: ClientID, found: ClientID },
     // #[error("the data for key `{0}` is not available")]
     // Redaction(String),
     // #[error("invalid header (expected {expected:?}, found {found:?})")]
diff --git a/crates/loro-core/src/fuzz/recursive.rs b/crates/loro-core/src/fuzz/recursive.rs
index f6ae955e..b5f021c4 100644
--- a/crates/loro-core/src/fuzz/recursive.rs
+++ b/crates/loro-core/src/fuzz/recursive.rs
@@ -350,7 +350,9 @@ impl Actionable for Vec<Actor> {
                         container.insert(&actor.loro, &key.to_string(), *i);
                     }
                     FuzzValue::Container(c) => {
-                        let new = container.insert_obj(&actor.loro, &key.to_string(), *c);
+                        let new = container
+                            .insert_obj(&actor.loro, &key.to_string(), *c)
+                            .unwrap();
                         actor.add_new_container(new);
                     }
                 }
@@ -380,7 +382,9 @@ impl Actionable for Vec<Actor> {
                         container.insert(&actor.loro, *key as usize, *i);
                     }
                     FuzzValue::Container(c) => {
-                        let new = container.insert_obj(&actor.loro, *key as usize, *c);
+                        let new = container
+                            .insert_obj(&actor.loro, *key as usize, *c)
+                            .unwrap();
                         actor.add_new_container(new)
                     }
                 }
diff --git a/crates/loro-core/src/value.rs b/crates/loro-core/src/value.rs
index c160fbe8..89bf683b 100644
--- a/crates/loro-core/src/value.rs
+++ b/crates/loro-core/src/value.rs
@@ -148,9 +148,13 @@ impl From<ContainerID> for LoroValue {
 pub mod wasm {
     use fxhash::FxHashMap;
     use js_sys::{Array, Object};
+    use wasm_bindgen::prelude::*;
     use wasm_bindgen::{JsCast, JsValue, __rt::IntoJsResult};
 
-    use crate::LoroValue;
+    use crate::{container::ContainerID as _ContainerID, LoroValue};
+
+    #[wasm_bindgen]
+    pub struct ContainerID(_ContainerID);
 
     pub fn convert(value: LoroValue) -> JsValue {
         match value {
@@ -176,8 +180,10 @@ pub mod wasm {
 
                 map.into_js_result().unwrap()
             }
-            LoroValue::Unresolved(_) => {
-                unreachable!()
+            LoroValue::Unresolved(container_id) => {
+                // FIXME:
+                // serde_wasm_bindgen::to_value(&container_id).unwrap()
+                ContainerID(*container_id).into()
             }
         }
     }
diff --git a/crates/loro-core/tests/test.rs b/crates/loro-core/tests/test.rs
index b884c9b5..07c052e0 100644
--- a/crates/loro-core/tests/test.rs
+++ b/crates/loro-core/tests/test.rs
@@ -10,13 +10,13 @@ fn example() {
 
     let mut doc = LoroCore::default();
     let mut list = doc.get_list("list");
-    list.insert(&doc, 0, 123);
-    let map_id = list.insert_obj(&doc, 1, ContainerType::Map);
+    list.insert(&doc, 0, 123).unwrap();
+    let map_id = list.insert_obj(&doc, 1, ContainerType::Map).unwrap();
     let mut map = doc.get_map(map_id);
-    let text = map.insert_obj(&doc, "map_b", ContainerType::Text);
+    let text = map.insert_obj(&doc, "map_b", ContainerType::Text).unwrap();
     let mut text = doc.get_text(text);
-    text.insert(&doc, 0, "world!");
-    text.insert(&doc, 0, "hello ");
+    text.insert(&doc, 0, "world!").unwrap();
+    text.insert(&doc, 0, "hello ").unwrap();
     assert_eq!(
         r#"[123,{"map_b":"hello world!"}]"#,
         list.get_value_deep(&doc).to_json()
@@ -30,11 +30,17 @@ fn list() {
     let mut loro_b = LoroCore::default();
     let mut list_a = loro_a.get_list("list");
     let mut list_b = loro_b.get_list("list");
-    list_a.insert_batch(&loro_a, 0, vec![12.into(), "haha".into()]);
-    list_b.insert_batch(&loro_b, 0, vec![123.into(), "kk".into()]);
-    let map_id = list_b.insert_obj(&loro_b, 1, loro_core::ContainerType::Map);
+    list_a
+        .insert_batch(&loro_a, 0, vec![12.into(), "haha".into()])
+        .unwrap();
+    list_b
+        .insert_batch(&loro_b, 0, vec![123.into(), "kk".into()])
+        .unwrap();
+    let map_id = list_b
+        .insert_obj(&loro_b, 1, loro_core::ContainerType::Map)
+        .unwrap();
     let mut map = loro_b.get_map(map_id);
-    map.insert(&loro_b, "map_b", 123);
+    map.insert(&loro_b, "map_b", 123).unwrap();
     println!("{}", list_a.get_value().to_json());
     println!("{}", list_b.get_value().to_json());
     loro_b.import(loro_a.export(loro_b.vv()));
@@ -49,7 +55,7 @@ fn list() {
 fn map() {
     let mut loro = LoroCore::new(Default::default(), Some(10));
     let mut root = loro.get_map("root");
-    root.insert(&loro, "haha", 1.2);
+    root.insert(&loro, "haha", 1.2).unwrap();
     let value = root.get_value();
     assert_eq!(value.as_map().unwrap().len(), 1);
     assert_eq!(
@@ -62,7 +68,9 @@ fn map() {
             .unwrap(),
         1.2
     );
-    let map_id = root.insert_obj(&loro, "map", loro_core::ContainerType::Map);
+    let map_id = root
+        .insert_obj(&loro, "map", loro_core::ContainerType::Map)
+        .unwrap();
     drop(root);
     let mut sub_map = loro.get_map(&map_id);
     sub_map.insert(&loro, "sub", false);
@@ -93,9 +101,9 @@ fn map() {
 fn two_client_text_sync() {
     let mut store = LoroCore::new(Default::default(), Some(10));
     let mut text_container = store.get_text("haha");
-    text_container.insert(&store, 0, "012");
-    text_container.insert(&store, 1, "34");
-    text_container.insert(&store, 1, "56");
+    text_container.insert(&store, 0, "012").unwrap();
+    text_container.insert(&store, 1, "34").unwrap();
+    text_container.insert(&store, 1, "56").unwrap();
     let value = text_container.get_value();
     let value = value.as_string().unwrap();
     assert_eq!(&**value, "0563412");
@@ -110,8 +118,8 @@ fn two_client_text_sync() {
     let value = value.as_string().unwrap();
     assert_eq!(&**value, "0563412");
 
-    text_container.delete(&store_b, 0, 2);
-    text_container.insert(&store_b, 4, "789");
+    text_container.delete(&store_b, 0, 2).unwrap();
+    text_container.insert(&store_b, 4, "789").unwrap();
     let value = text_container.get_value();
     let value = value.as_string().unwrap();
     assert_eq!(&**value, "63417892");
@@ -122,8 +130,8 @@ fn two_client_text_sync() {
     let value = text_container.get_value();
     let value = value.as_string().unwrap();
     assert_eq!(&**value, "63417892");
-    text_container.delete(&store, 0, 8);
-    text_container.insert(&store, 0, "abc");
+    text_container.delete(&store, 0, 8).unwrap();
+    text_container.insert(&store, 0, "abc").unwrap();
     let value = text_container.get_value();
     let value = value.as_string().unwrap();
     assert_eq!(&**value, "abc");
@@ -143,8 +151,8 @@ fn test_recursive_should_panic() {
     let mut store_b = LoroCore::new(Default::default(), Some(2));
     let mut text_a = store_a.get_text("text_a");
     let mut text_b = store_b.get_text("text_b");
-    text_a.insert(&store_a, 0, "012");
-    text_b.insert(&store_a, 1, "34");
+    text_a.insert(&store_a, 0, "012").unwrap();
+    text_b.insert(&store_a, 1, "34").unwrap();
 }
 
 #[ctor]
diff --git a/crates/loro-wasm/deno.lock b/crates/loro-wasm/deno.lock
index 86befe69..adc978c5 100644
--- a/crates/loro-wasm/deno.lock
+++ b/crates/loro-wasm/deno.lock
@@ -12,6 +12,10 @@
     "https://deno.land/std@0.105.0/path/posix.ts": "b81974c768d298f8dcd2c720229639b3803ca4a241fa9a355c762fa2bc5ef0c1",
     "https://deno.land/std@0.105.0/path/separator.ts": "8fdcf289b1b76fd726a508f57d3370ca029ae6976fcde5044007f062e643ff1c",
     "https://deno.land/std@0.105.0/path/win32.ts": "f4a3d4a3f2c9fe894da046d5eac48b5e789a0ebec5152b2c0985efe96a9f7ae1",
+    "https://deno.land/std@0.165.0/fmt/colors.ts": "9e36a716611dcd2e4865adea9c4bec916b5c60caad4cdcdc630d4974e6bb8bd4",
+    "https://deno.land/std@0.165.0/testing/_diff.ts": "a23e7fc2b4d8daa3e158fa06856bedf5334ce2a2831e8bf9e509717f455adb2c",
+    "https://deno.land/std@0.165.0/testing/_format.ts": "cd11136e1797791045e639e9f0f4640d5b4166148796cad37e6ef75f7d7f3832",
+    "https://deno.land/std@0.165.0/testing/asserts.ts": "1e340c589853e82e0807629ba31a43c84ebdcdeca910c4a9705715dfdb0f5ce8",
     "https://deno.land/x/dirname@1.1.2/mod.ts": "4029ca6b49da58d262d65f826ba9b3a89cc0b92a94c7220d5feb7bd34e498a54",
     "https://deno.land/x/dirname@1.1.2/types.ts": "c1ed1667545bc4b1d69bdb2fc26a5fa8edae3a56e3081209c16a408a322a2319",
     "https://lra6z45nakk5lnu3yjchp7tftsdnwwikwr65ocha5eojfnlgu4sa.arweave.net/XEHs860CldW2m8JEd_5lnIbbWQq0fdcI4OkckrVmpyQ/_util/assert.ts": "e1f76e77c5ccb5a8e0dbbbe6cce3a56d2556c8cb5a9a8802fc9565af72462149",
diff --git a/crates/loro-wasm/deno_test/test.ts b/crates/loro-wasm/deno_test/test.ts
index e64f2328..adf36813 100644
--- a/crates/loro-wasm/deno_test/test.ts
+++ b/crates/loro-wasm/deno_test/test.ts
@@ -23,7 +23,9 @@ Deno.test({
   b.set(loro, "ab", 123);
   console.log(b.value);
   console.log(a.value);
+  
   const bText = b.getText(loro, "hh");
+
   await t.step("getValueDeep", () => {
     bText.insert(loro, 0, "hello world Text");
     assertEquals(b.getValueDeep(loro), { ab: 123, hh: "hello world Text" });
@@ -37,8 +39,12 @@ Deno.test({
   });
   
   await t.step("get value error", () => {
-    assertThrows(()=>{
-      const _ = bText.value;
-    });
+    // assertThrows(()=>{
+      const map = loro.getMap("map");
+      const list = map.getList(loro, "list");
+      list.insert(loro, 0, 123);
+      console.log(map.value);
+      
+    // });
   });
 });
diff --git a/crates/loro-wasm/src/lib.rs b/crates/loro-wasm/src/lib.rs
index 93fdfbda..a9a2d6fb 100644
--- a/crates/loro-wasm/src/lib.rs
+++ b/crates/loro-wasm/src/lib.rs
@@ -18,6 +18,8 @@ pub fn set_panic_hook() {
     console_error_panic_hook::set_once();
 }
 
+type JsResult<T> = Result<T, JsError>;
+
 #[wasm_bindgen]
 pub struct Loro(LoroCore);
 
@@ -43,13 +45,13 @@ impl Loro {
     }
 
     #[wasm_bindgen(js_name = "getText")]
-    pub fn get_text(&mut self, name: &str) -> Result<LoroText, JsValue> {
+    pub fn get_text(&mut self, name: &str) -> JsResult<LoroText> {
         let text = self.0.get_text(name);
         Ok(LoroText(text))
     }
 
     #[wasm_bindgen(js_name = "getMap")]
-    pub fn get_map(&mut self, name: &str) -> Result<LoroMap, JsValue> {
+    pub fn get_map(&mut self, name: &str) -> JsResult<LoroMap> {
         let map = self.0.get_map(name);
         Ok(LoroMap(map))
     }
@@ -60,16 +62,18 @@ pub struct LoroText(Text);
 
 #[wasm_bindgen]
 impl LoroText {
-    pub fn insert(&mut self, ctx: &Loro, index: usize, content: &str) {
-        self.0.insert(ctx.deref(), index, content);
+    pub fn insert(&mut self, ctx: &Loro, index: usize, content: &str) -> JsResult<()> {
+        self.0.insert(ctx.deref(), index, content)?;
+        Ok(())
     }
 
-    pub fn delete(&mut self, ctx: &Loro, index: usize, len: usize) {
-        self.0.delete(ctx.deref(), index, len);
+    pub fn delete(&mut self, ctx: &Loro, index: usize, len: usize) -> JsResult<()> {
+        self.0.delete(ctx.deref(), index, len)?;
+        Ok(())
     }
 
     #[wasm_bindgen(js_name = "value", method, getter)]
-    pub fn get_value(&mut self) -> String {
+    pub fn get_value(&self) -> String {
         self.0.get_value().as_string().unwrap().to_string()
     }
 }
@@ -80,43 +84,54 @@ pub struct LoroMap(Map);
 #[wasm_bindgen]
 impl LoroMap {
     #[wasm_bindgen(js_name = "set")]
-    pub fn insert(&mut self, ctx: &Loro, key: &str, value: JsValue) {
-        self.0.insert(ctx.deref(), key, value);
+    pub fn insert(&mut self, ctx: &Loro, key: &str, value: JsValue) -> JsResult<()> {
+        self.0.insert(ctx.deref(), key, value)?;
+        Ok(())
     }
 
-    pub fn delete(&mut self, ctx: &Loro, key: &str) {
-        self.0.delete(ctx.deref(), key);
+    pub fn delete(&mut self, ctx: &Loro, key: &str) -> JsResult<()> {
+        self.0.delete(ctx.deref(), key)?;
+        Ok(())
+    }
+
+    pub fn get(&self, key: &str) -> JsValue {
+        self.0.get(key).into()
     }
 
     #[wasm_bindgen(js_name = "value", method, getter)]
-    pub fn get_value(&mut self) -> JsValue {
+    pub fn get_value(&self) -> JsValue {
+        // TODO: if unresolved, return a container ID
         self.0.get_value().into()
     }
 
     #[wasm_bindgen(js_name = "getValueDeep")]
-    pub fn get_value_deep(&mut self, ctx: &Loro) -> JsValue {
+    pub fn get_value_deep(&self, ctx: &Loro) -> JsValue {
         self.0.get_value_deep(ctx.deref()).into()
     }
 
     #[wasm_bindgen(js_name = "getText")]
-    pub fn get_text(&mut self, ctx: &mut Loro, key: &str) -> LoroText {
-        let id = self.0.insert_obj(&ctx.0, key, ContainerType::Text);
+    pub fn get_text(&mut self, ctx: &mut Loro, key: &str) -> JsResult<LoroText> {
+        let id = self.0.insert_obj(&ctx.0, key, ContainerType::Text)?;
         let text = ctx.deref().get_container(&id).unwrap();
-        LoroText(Text::from_instance(text, ctx.deref().client_id()))
+        Ok(LoroText(Text::from_instance(text, ctx.deref().client_id())))
     }
 
     #[wasm_bindgen(js_name = "getMap")]
-    pub fn get_map(&mut self, ctx: &mut Loro, key: &str) -> LoroMap {
-        let id = self.0.insert_obj(ctx.deref_mut(), key, ContainerType::Map);
+    pub fn get_map(&mut self, ctx: &mut Loro, key: &str) -> JsResult<LoroMap> {
+        let id = self
+            .0
+            .insert_obj(ctx.deref_mut(), key, ContainerType::Map)?;
         let map = ctx.deref().get_container(&id).unwrap();
-        LoroMap(Map::from_instance(map, ctx.deref().client_id()))
+        Ok(LoroMap(Map::from_instance(map, ctx.deref().client_id())))
     }
 
     #[wasm_bindgen(js_name = "getList")]
-    pub fn get_list(&mut self, ctx: &mut Loro, key: &str) -> LoroList {
-        let id = self.0.insert_obj(ctx.deref_mut(), key, ContainerType::List);
+    pub fn get_list(&mut self, ctx: &mut Loro, key: &str) -> JsResult<LoroList> {
+        let id = self
+            .0
+            .insert_obj(ctx.deref_mut(), key, ContainerType::List)?;
         let list = ctx.deref().get_container(&id).unwrap();
-        LoroList(List::from_instance(list, ctx.deref().client_id()))
+        Ok(LoroList(List::from_instance(list, ctx.deref().client_id())))
     }
 }
 
@@ -125,13 +140,18 @@ pub struct LoroList(List);
 
 #[wasm_bindgen]
 impl LoroList {
-    #[wasm_bindgen(js_name = "set")]
-    pub fn insert(&mut self, ctx: &Loro, index: usize, value: JsValue) {
-        self.0.insert(ctx.deref(), index, value);
+    pub fn insert(&mut self, ctx: &Loro, index: usize, value: JsValue) -> JsResult<()> {
+        self.0.insert(ctx.deref(), index, value)?;
+        Ok(())
     }
 
-    pub fn delete(&mut self, ctx: &Loro, index: usize, len: usize) {
-        self.0.delete(ctx.deref(), index, len);
+    pub fn delete(&mut self, ctx: &Loro, index: usize, len: usize) -> JsResult<()> {
+        self.0.delete(ctx.deref(), index, len)?;
+        Ok(())
+    }
+
+    pub fn get(&self, index: usize) -> JsValue {
+        self.0.get(index).into()
     }
 
     #[wasm_bindgen(js_name = "value", method, getter)]
@@ -140,35 +160,35 @@ impl LoroList {
     }
 
     #[wasm_bindgen(js_name = "getValueDeep")]
-    pub fn get_value_deep(&mut self, ctx: &Loro) -> JsValue {
+    pub fn get_value_deep(&self, ctx: &Loro) -> JsValue {
         self.0.get_value_deep(ctx.deref()).into()
     }
 
     #[wasm_bindgen(js_name = "getText")]
-    pub fn get_text(&mut self, ctx: &mut Loro, index: usize) -> LoroText {
+    pub fn get_text(&mut self, ctx: &mut Loro, index: usize) -> JsResult<LoroText> {
         let id = self
             .0
-            .insert_obj(ctx.deref_mut(), index, ContainerType::Text);
+            .insert_obj(ctx.deref_mut(), index, ContainerType::Text)?;
         let text = ctx.deref().get_container(&id).unwrap();
-        LoroText(Text::from_instance(text, ctx.deref().client_id()))
+        Ok(LoroText(Text::from_instance(text, ctx.deref().client_id())))
     }
 
     #[wasm_bindgen(js_name = "getMap")]
-    pub fn get_map(&mut self, ctx: &mut Loro, index: usize) -> LoroMap {
+    pub fn get_map(&mut self, ctx: &mut Loro, index: usize) -> JsResult<LoroMap> {
         let id = self
             .0
-            .insert_obj(ctx.deref_mut(), index, ContainerType::Map);
+            .insert_obj(ctx.deref_mut(), index, ContainerType::Map)?;
         let map = ctx.deref().get_container(&id).unwrap();
-        LoroMap(Map::from_instance(map, ctx.deref().client_id()))
+        Ok(LoroMap(Map::from_instance(map, ctx.deref().client_id())))
     }
 
     #[wasm_bindgen(js_name = "getList")]
-    pub fn get_list(&mut self, ctx: &mut Loro, index: usize) -> LoroList {
+    pub fn get_list(&mut self, ctx: &mut Loro, index: usize) -> JsResult<LoroList> {
         let id = self
             .0
-            .insert_obj(ctx.deref_mut(), index, ContainerType::List);
+            .insert_obj(ctx.deref_mut(), index, ContainerType::List)?;
         let list = ctx.deref().get_container(&id).unwrap();
-        LoroList(List::from_instance(list, ctx.deref().client_id()))
+        Ok(LoroList(List::from_instance(list, ctx.deref().client_id())))
     }
 }