diff --git a/README.md b/README.md
index 48c4c7fc..2a6cc838 100644
--- a/README.md
+++ b/README.md
@@ -40,9 +40,6 @@
 
 https://github.com/loro-dev/loro/assets/18425020/fe246c47-a120-44b3-91d4-1e7232a5b4ac
 
-
-> ⚠️ **Notice**: The current API and encoding schema of Loro are **experimental** and **subject to change**. You should not use it in production. 
-
 Loro is a [CRDTs(Conflict-free Replicated Data Types)](https://crdt.tech/) library that makes building [local-first apps][local-first] easier. It is currently available for JavaScript (via WASM) and Rust developers. 
 
 Explore our vision in our blog: [**✨ Reimagine State Management with CRDTs**](https://loro.dev/blog/loro-now-open-source).
diff --git a/crates/loro-common/src/error.rs b/crates/loro-common/src/error.rs
index cd838639..f7e843bb 100644
--- a/crates/loro-common/src/error.rs
+++ b/crates/loro-common/src/error.rs
@@ -68,10 +68,12 @@ pub enum LoroError {
     UndoWithDifferentPeerId { expected: PeerID, actual: PeerID },
     #[error("The input JSON schema is invalid")]
     InvalidJsonSchema,
-    #[error("Cannot insert or delete utf-8 in the middle of the codepoint in Unicode.")]
+    #[error("Cannot insert or delete utf-8 in the middle of the codepoint in Unicode")]
     UTF8InUnicodeCodePoint { pos: usize },
-    #[error("Cannot insert or delete utf-16 in the middle of the codepoint in Unicode.")]
+    #[error("Cannot insert or delete utf-16 in the middle of the codepoint in Unicode")]
     UTF16InUnicodeCodePoint { pos: usize },
+    #[error("The end index cannot be less than the start index")]
+    EndIndexLessThanStartIndex { start: usize, end: usize },
 }
 
 #[derive(Error, Debug)]
diff --git a/crates/loro-internal/src/container/richtext/richtext_state.rs b/crates/loro-internal/src/container/richtext/richtext_state.rs
index 9550dad2..9302a2c1 100644
--- a/crates/loro-internal/src/container/richtext/richtext_state.rs
+++ b/crates/loro-internal/src/container/richtext/richtext_state.rs
@@ -582,6 +582,17 @@ impl CanRemove for RichtextStateChunk {
     }
 }
 
+//TODO: start/end can be scanned in one loop, but now it takes twice the time
+fn unicode_slice(s: &str, start_index: usize, end_index: usize) -> Result<&str, ()> {
+    let (Some(start), Some(end)) = (
+        unicode_to_utf8_index(s, start_index),
+        unicode_to_utf8_index(s, end_index),
+    ) else {
+        return Err(());
+    };
+    Ok(&s[start..end])
+}
+
 pub(crate) fn unicode_to_utf8_index(s: &str, unicode_index: usize) -> Option<usize> {
     let mut current_unicode_index = 0;
     for (byte_index, _) in s.char_indices() {
@@ -1626,6 +1637,27 @@ impl RichtextState {
         self.style_ranges.as_mut().unwrap()
     }
 
+    pub(crate) fn get_char_by_event_index(&self, pos: usize) -> Result<char, ()> {
+        let cursor = self.tree.query::<EventIndexQuery>(&pos).unwrap().cursor;
+        let Some(str) = &self.tree.get_elem(cursor.leaf) else {
+            return Err(());
+        };
+        if cfg!(not(feature = "wasm")) {
+            let mut char_iter = str.as_str().unwrap().chars();
+            match &mut char_iter.nth(cursor.offset) {
+                Some(c) => Ok(*c),
+                None => Err(()),
+            }
+        } else {
+            let s = str.as_str().unwrap();
+            let utf16offset = unicode_to_utf16_index(s, cursor.offset).unwrap();
+            match s.encode_utf16().nth(utf16offset) {
+                Some(c) => Ok(std::char::from_u32(c as u32).unwrap()),
+                None => Err(()),
+            }
+        }
+    }
+
     /// Find the best insert position based on algorithm similar to Peritext.
     /// The result is only different from `query` when there are style anchors around the insert pos.
     /// Returns the right neighbor of the insert pos and the entity index.
@@ -1874,6 +1906,54 @@ impl RichtextState {
         Ok(ans)
     }
 
+    pub(crate) fn get_text_slice_by_event_index(
+        &self,
+        pos: usize,
+        len: usize,
+    ) -> LoroResult<String> {
+        if self.tree.is_empty() {
+            return Ok(String::new());
+        }
+
+        if len == 0 {
+            return Ok(String::new());
+        }
+
+        if pos + len > self.len_event() {
+            return Err(LoroError::OutOfBound {
+                pos: pos + len,
+                len: self.len_event(),
+                info: format!("Position: {}:{}", file!(), line!()).into_boxed_str(),
+            });
+        }
+
+        let mut ans = String::new();
+        let (start, end) = (
+            self.tree.query::<EventIndexQuery>(&pos).unwrap().cursor,
+            self.tree
+                .query::<EventIndexQuery>(&(pos + len))
+                .unwrap()
+                .cursor,
+        );
+
+        for span in self.tree.iter_range(start..end) {
+            let start = span.start.unwrap_or(0);
+            let end = span.end.unwrap_or(span.elem.rle_len());
+            if end == 0 {
+                break;
+            }
+
+            if let RichtextStateChunk::Text(s) = span.elem {
+                match unicode_slice(&s.as_str(), start, end) {
+                    Ok(x) => ans.push_str(&x),
+                    Err(()) => return Err(LoroError::UTF16InUnicodeCodePoint { pos: pos + len }),
+                }
+            }
+        }
+
+        Ok(ans)
+    }
+
     // PERF: can be splitted into two methods. One is without cursor_to_event_index
     // PERF: can be speed up a lot by detecting whether the range is in a single leaf first
     /// This is used to accept changes from DiffCalculator
diff --git a/crates/loro-internal/src/handler.rs b/crates/loro-internal/src/handler.rs
index 5ea0a0b0..8966a305 100644
--- a/crates/loro-internal/src/handler.rs
+++ b/crates/loro-internal/src/handler.rs
@@ -1363,6 +1363,80 @@ impl TextHandler {
         }
     }
 
+    /// `pos` is a Event Index:
+    ///
+    /// - if feature="wasm", pos is a UTF-16 index
+    /// - if feature!="wasm", pos is a Unicode index
+    pub fn char_at(&self, pos: usize) -> LoroResult<char> {
+        if pos >= self.len_event() {
+            return Err(LoroError::OutOfBound {
+                pos: pos,
+                len: self.len_event(),
+                info: format!("Position: {}:{}", file!(), line!()).into_boxed_str(),
+            });
+        }
+        if let Ok(c) = match &self.inner {
+            MaybeDetached::Detached(t) => {
+                let t = t.try_lock().unwrap();
+                t.value.get_char_by_event_index(pos)
+            }
+            MaybeDetached::Attached(a) => a.with_state(|state| {
+                state
+                    .as_richtext_state_mut()
+                    .unwrap()
+                    .get_char_by_event_index(pos)
+            }),
+        } {
+            Ok(c)
+        } else {
+            Err(LoroError::OutOfBound {
+                pos: pos,
+                len: self.len_event(),
+                info: format!("Position: {}:{}", file!(), line!()).into_boxed_str(),
+            })
+        }
+    }
+
+    /// `start_index` and `end_index` are Event Index:
+    ///
+    /// - if feature="wasm", pos is a UTF-16 index
+    /// - if feature!="wasm", pos is a Unicode index
+    ///
+    pub fn slice(&self, start_index: usize, end_index: usize) -> LoroResult<String> {
+        if end_index < start_index {
+            return Err(LoroError::EndIndexLessThanStartIndex {
+                start: start_index,
+                end: end_index,
+            });
+        }
+        match &self.inner {
+            MaybeDetached::Detached(t) => {
+                let t = t.try_lock().unwrap();
+                t.value
+                    .get_text_slice_by_event_index(start_index, end_index - start_index)
+            }
+            MaybeDetached::Attached(a) => a.with_state(|state| {
+                state
+                    .as_richtext_state_mut()
+                    .unwrap()
+                    .get_text_slice_by_event_index(start_index, end_index - start_index)
+            }),
+        }
+    }
+
+    /// `pos` is a Event Index:
+    ///
+    /// - if feature="wasm", pos is a UTF-16 index
+    /// - if feature!="wasm", pos is a Unicode index
+    ///
+    /// This method requires auto_commit to be enabled.
+    pub fn splice(&self, pos: usize, len: usize, s: &str) -> LoroResult<String> {
+        let x = self.slice(pos, pos + len)?;
+        self.delete(pos, len)?;
+        self.insert(pos, s)?;
+        Ok(x)
+    }
+
     /// `pos` is a Event Index:
     ///
     /// - if feature="wasm", pos is a UTF-16 index
@@ -3541,7 +3615,14 @@ impl MapHandler {
     pub fn len(&self) -> usize {
         match &self.inner {
             MaybeDetached::Detached(m) => m.try_lock().unwrap().value.len(),
-            MaybeDetached::Attached(a) => a.with_state(|state| state.as_map_state().unwrap().len()),
+            MaybeDetached::Attached(a) => a.with_state(|state| {
+                state
+                    .as_map_state()
+                    .unwrap()
+                    .iter()
+                    .filter(|&(_, v)| v.value.is_some())
+                    .count()
+            }),
         }
     }
 
diff --git a/crates/loro-internal/src/state/richtext_state.rs b/crates/loro-internal/src/state/richtext_state.rs
index d381c280..bfbbac0e 100644
--- a/crates/loro-internal/src/state/richtext_state.rs
+++ b/crates/loro-internal/src/state/richtext_state.rs
@@ -96,7 +96,19 @@ impl RichtextState {
         }
     }
 
-    pub(crate) fn iter(&mut self, mut callback: impl FnMut(&str) -> bool) {
+    pub(crate) fn get_text_slice_by_event_index(
+        &mut self,
+        pos: usize,
+        len: usize,
+    ) -> LoroResult<String> {
+        self.state.get_mut().get_text_slice_by_event_index(pos, len)
+    }
+
+    pub(crate) fn get_char_by_event_index(&mut self, pos: usize) -> Result<char, ()> {
+        self.state.get_mut().get_char_by_event_index(pos)
+    }
+
+    pub(crate) fn iter(&mut self, mut callback: impl FnMut(&str) -> bool) -> () {
         for span in self.state.get_mut().iter() {
             if !callback(span.text.as_str()) {
                 return;
diff --git a/crates/loro-internal/tests/test.rs b/crates/loro-internal/tests/test.rs
index b1e2e642..8078fef1 100644
--- a/crates/loro-internal/tests/test.rs
+++ b/crates/loro-internal/tests/test.rs
@@ -1106,6 +1106,103 @@ fn test_delete_utf8_panic_out_bound_len() {
 }
 
 #[test]
+fn test_char_at() {
+    let doc = LoroDoc::new_auto_commit();
+    let text = doc.get_text("text");
+    text.insert(0, "Herld").unwrap();
+    text.insert(2, "llo Wo").unwrap();
+    assert_eq!(text.char_at(0).unwrap(), 'H');
+    assert_eq!(text.char_at(1).unwrap(), 'e');
+    assert_eq!(text.char_at(2).unwrap(), 'l');
+    assert_eq!(text.char_at(3).unwrap(), 'l');
+    let err = text.char_at(15).unwrap_err();
+    assert!(matches!(err, loro_common::LoroError::OutOfBound { .. }))
+}
+
+#[test]
+fn test_char_at_detached() {
+    let text = TextHandler::new_detached();
+    text.insert(0, "Herld").unwrap();
+    text.insert(2, "llo Wo").unwrap();
+    assert_eq!(text.char_at(0).unwrap(), 'H');
+    assert_eq!(text.char_at(1).unwrap(), 'e');
+    assert_eq!(text.char_at(2).unwrap(), 'l');
+    assert_eq!(text.char_at(3).unwrap(), 'l');
+    let err = text.char_at(15).unwrap_err();
+    assert!(matches!(err, loro_common::LoroError::OutOfBound { .. }))
+}
+
+#[test]
+fn test_char_at_wchar() {
+    let doc = LoroDoc::new_auto_commit();
+    let text = doc.get_text("text");
+    text.insert(0, "你好").unwrap();
+    text.insert(1, "世界").unwrap();
+    assert_eq!(text.char_at(0).unwrap(), '你');
+    assert_eq!(text.char_at(1).unwrap(), '世');
+    assert_eq!(text.char_at(2).unwrap(), '界');
+    assert_eq!(text.char_at(3).unwrap(), '好');
+    let err = text.char_at(5).unwrap_err();
+    assert!(matches!(err, loro_common::LoroError::OutOfBound { .. }))
+}
+
+#[test]
+fn test_text_slice() {
+    let doc = LoroDoc::new_auto_commit();
+    let text = doc.get_text("text");
+    text.insert(0, "Hello").unwrap();
+    text.insert(1, "World").unwrap();
+    assert_eq!(text.slice(0, 4).unwrap(), "HWor");
+    assert_eq!(text.slice(0, 1).unwrap(), "H");
+}
+
+#[test]
+fn test_text_slice_detached() {
+    let text = TextHandler::new_detached();
+    text.insert(0, "Herld").unwrap();
+    text.insert(2, "llo Wo").unwrap();
+    assert_eq!(text.slice(0, 4).unwrap(), "Hell");
+    assert_eq!(text.slice(0, 1).unwrap(), "H");
+}
+
+#[test]
+fn test_text_slice_wchar() {
+    let doc = LoroDoc::new_auto_commit();
+    let text = doc.get_text("text");
+    text.insert(0, "你好").unwrap();
+    text.insert(1, "世界").unwrap();
+    assert_eq!(text.slice(0, 3).unwrap(), "你世界");
+}
+
+#[test]
+#[should_panic]
+fn test_text_slice_end_index_less_than_start() {
+    let doc = LoroDoc::new_auto_commit();
+    let text = doc.get_text("text");
+    text.insert(0, "你好").unwrap();
+    text.insert(1, "世界").unwrap();
+    text.slice(2, 1).unwrap();
+}
+
+#[test]
+#[should_panic]
+fn test_text_slice_out_of_bound() {
+    let doc = LoroDoc::new_auto_commit();
+    let text = doc.get_text("text");
+    text.insert(0, "你好").unwrap();
+    text.insert(1, "世界").unwrap();
+    text.slice(1, 10).unwrap();
+}
+
+#[test]
+fn test_text_splice() {
+    let doc = LoroDoc::new_auto_commit();
+    let text = doc.get_text("text");
+    text.insert(0, "你好").unwrap();
+    assert_eq!(text.splice(1, 1, "世界").unwrap(), "好");
+    assert_eq!(text.to_string(), "你世界");
+}
+
 fn test_text_iter() {
     let mut str = String::new();
     let doc = LoroDoc::new_auto_commit();
diff --git a/crates/loro-wasm/CHANGELOG.md b/crates/loro-wasm/CHANGELOG.md
index c51bc932..e7c766dc 100644
--- a/crates/loro-wasm/CHANGELOG.md
+++ b/crates/loro-wasm/CHANGELOG.md
@@ -1,5 +1,34 @@
 # Changelog
 
+## 0.16.7
+
+### Patch Changes
+
+- 45c98d5: Better text APIs and bug fixes
+
+  ### 🚀 Features
+
+  - Add insert_utf8 and delete_utf8 for Rust Text API (#396)
+  - Add text iter (#400)
+  - Add more text api (#398)
+
+  ### 🐛 Bug Fixes
+
+  - Tree undo when processing deleted node (#399)
+  - Tree diff calc children should be sorted by idlp (#401)
+  - When computing the len of the map, do not count elements that are None (#402)
+
+  ### 📚 Documentation
+
+  - Update wasm docs
+  - Rm experimental warning
+
+  ### ⚙️ Miscellaneous Tasks
+
+  - Update fuzz config
+  - Pnpm
+  - Rename position to fractional_index (#381)
+
 ## 0.16.6
 
 ### Patch Changes
diff --git a/crates/loro-wasm/package.json b/crates/loro-wasm/package.json
index 67c620b7..5579f4f9 100644
--- a/crates/loro-wasm/package.json
+++ b/crates/loro-wasm/package.json
@@ -1,6 +1,6 @@
 {
   "name": "loro-wasm",
-  "version": "0.16.6",
+  "version": "0.16.7",
   "description": "Loro CRDTs is a high-performance CRDT framework that makes your app state synchronized, collaborative and maintainable effortlessly.",
   "keywords": [
     "crdt",
diff --git a/crates/loro-wasm/src/lib.rs b/crates/loro-wasm/src/lib.rs
index 49fbf9ed..8ef23d0c 100644
--- a/crates/loro-wasm/src/lib.rs
+++ b/crates/loro-wasm/src/lib.rs
@@ -1541,6 +1541,61 @@ impl LoroText {
         Ok(())
     }
 
+    /// Get a string slice.
+    ///
+    /// @example
+    /// ```ts
+    /// import { Loro } from "loro-crdt";
+    ///
+    /// const doc = new Loro();
+    /// const text = doc.getText("text");
+    /// text.insert(0, "Hello");
+    /// text.slice(0, 2); // "He"
+    /// ```
+    pub fn slice(&mut self, start_index: usize, end_index: usize) -> JsResult<String> {
+        match self.handler.slice(start_index, end_index) {
+            Ok(x) => Ok(x),
+            Err(x) => Err(x.into()),
+        }
+    }
+
+    /// Get the character at the given position.
+    ///
+    /// @example
+    /// ```ts
+    /// import { Loro } from "loro-crdt";
+    ///
+    /// const doc = new Loro();
+    /// const text = doc.getText("text");
+    /// text.insert(0, "Hello");
+    /// text.charAt(0); // "H"
+    /// ```
+    #[wasm_bindgen(js_name = "charAt")]
+    pub fn char_at(&mut self, pos: usize) -> JsResult<char> {
+        match self.handler.char_at(pos) {
+            Ok(x) => Ok(x),
+            Err(x) => Err(x.into()),
+        }
+    }
+
+    /// Delete and return the string at the given range and insert a string at the same position.
+    ///
+    /// @example
+    /// ```ts
+    /// import { Loro } from "loro-crdt";
+    ///
+    /// const doc = new Loro();
+    /// const text = doc.getText("text");
+    /// text.insert(0, "Hello");
+    /// text.splice(2, 3, "llo"); // "llo"
+    /// ```
+    pub fn splice(&mut self, pos: usize, len: usize, s: &str) -> JsResult<String> {
+        match self.handler.splice(pos, len, s) {
+            Ok(x) => Ok(x),
+            Err(x) => Err(x.into()),
+        }
+    }
+
     /// Insert some string at utf-8 index.
     ///
     /// @example
diff --git a/crates/loro/src/lib.rs b/crates/loro/src/lib.rs
index 9e40d245..64f6c7bb 100644
--- a/crates/loro/src/lib.rs
+++ b/crates/loro/src/lib.rs
@@ -1006,6 +1006,21 @@ impl LoroText {
         self.handler.delete_utf8(pos, len)
     }
 
+    /// Get a string slice at the given Unicode range
+    pub fn slice(&self, start_index: usize, end_index: usize) -> LoroResult<String> {
+        self.handler.slice(start_index, end_index)
+    }
+
+    /// Get the characters at given unicode position.
+    pub fn char_at(&self, pos: usize) -> LoroResult<char> {
+        self.handler.char_at(pos)
+    }
+
+    /// Delete specified character and insert string at the same position at given unicode position.
+    pub fn splice(&self, pos: usize, len: usize, s: &str) -> LoroResult<String> {
+        self.handler.splice(pos, len, s)
+    }
+
     /// Whether the text container is empty.
     pub fn is_empty(&self) -> bool {
         self.handler.is_empty()
diff --git a/crates/loro/tests/loro_rust_test.rs b/crates/loro/tests/loro_rust_test.rs
index acff0778..b07ffd5d 100644
--- a/crates/loro/tests/loro_rust_test.rs
+++ b/crates/loro/tests/loro_rust_test.rs
@@ -853,3 +853,20 @@ fn awareness() {
     );
     assert_eq!(b.get_all_states().get(&2).map(|x| x.state.clone()), None);
 }
+
+#[test]
+// https://github.com/loro-dev/loro/issues/397
+fn len_and_is_empty_inconsistency() {
+    let doc = LoroDoc::new();
+    let map = doc.get_map("map");
+    println!("{:#?}", map);
+    assert!(map.is_empty());
+    map.insert("leaf", 42i64).unwrap();
+    println!("{:#?}", map.get("leaf"));
+
+    assert_eq!(map.len(), 1);
+    map.delete("leaf").unwrap();
+    println!("{:#?}", map.get("leaf"));
+    assert_eq!(map.len(), 0);
+    assert!(map.is_empty());
+}
diff --git a/loro-js/CHANGELOG.md b/loro-js/CHANGELOG.md
index b3aee710..04882384 100644
--- a/loro-js/CHANGELOG.md
+++ b/loro-js/CHANGELOG.md
@@ -1,5 +1,37 @@
 # Changelog
 
+## 0.16.7
+
+### Patch Changes
+
+- 45c98d5: Better text APIs and bug fixes
+
+  ### 🚀 Features
+
+  - Add insert_utf8 and delete_utf8 for Rust Text API (#396)
+  - Add text iter (#400)
+  - Add more text api (#398)
+
+  ### 🐛 Bug Fixes
+
+  - Tree undo when processing deleted node (#399)
+  - Tree diff calc children should be sorted by idlp (#401)
+  - When computing the len of the map, do not count elements that are None (#402)
+
+  ### 📚 Documentation
+
+  - Update wasm docs
+  - Rm experimental warning
+
+  ### ⚙️ Miscellaneous Tasks
+
+  - Update fuzz config
+  - Pnpm
+  - Rename position to fractional_index (#381)
+
+- Updated dependencies [45c98d5]
+  - loro-wasm@0.16.7
+
 ## 0.16.6
 
 ### Patch Changes
diff --git a/loro-js/package.json b/loro-js/package.json
index 5b587db9..cedc187d 100644
--- a/loro-js/package.json
+++ b/loro-js/package.json
@@ -1,6 +1,6 @@
 {
   "name": "loro-crdt",
-  "version": "0.16.6",
+  "version": "0.16.7",
   "description": "Loro CRDTs is a high-performance CRDT framework that makes your app state synchronized, collaborative and maintainable effortlessly.",
   "keywords": [
     "crdt",
diff --git a/loro-js/tests/richtext.test.ts b/loro-js/tests/richtext.test.ts
index 9cfeb450..acdbbd5f 100644
--- a/loro-js/tests/richtext.test.ts
+++ b/loro-js/tests/richtext.test.ts
@@ -302,6 +302,35 @@ describe("richtext", () => {
     ]);
   });
 
+  it("Slice", () => {
+    const doc = new Loro();
+    const text = doc.getText('t');
+    text.insert(0, "你好");
+    expect(text.slice(0, 1)).toStrictEqual("你");
+  });
+
+  it("Slice emoji", () => {
+    const doc = new Loro();
+    const text = doc.getText('t');
+    text.insert(0, "😡😡😡");
+    expect(text.slice(0, 2)).toStrictEqual("😡");
+  });
+
+  it("CharAt", () => {
+    const doc = new Loro();
+    const text = doc.getText('t');
+    text.insert(0, "你好");
+    expect(text.charAt(1)).toStrictEqual("好");
+  });
+
+  it("Splice", () => {
+    const doc = new Loro();
+    const text = doc.getText('t');
+    text.insert(0, "你好");
+    expect(text.splice(1, 1, "我")).toStrictEqual("好");
+    expect(text.toString()).toStrictEqual("你我");
+  });
+
   it("Text iter", () => {
     const doc = new Loro();
     const text = doc.getText('t');