diff --git a/page/client.ts b/page/client.ts
index f23a17b..c19820e 100644
--- a/page/client.ts
+++ b/page/client.ts
@@ -209,3 +209,45 @@ export function redrawPreeditUnderline() {
 export function hasPreedit() {
   return !!preedit
 }
+
+export function deleteSurroundingText(offset: number, size: number) {
+  const input = getInputElement()
+  if (!input) {
+    return
+  }
+
+  const text = input.value
+  const jsCursor = input.selectionStart!
+  const chars = [...text]
+
+  let charCursor = 0
+  let currentJsIndex = 0
+  for (const char of chars) {
+    if (currentJsIndex >= jsCursor) {
+      break
+    }
+    currentJsIndex += char.length
+    charCursor++
+  }
+
+  const startCharIndex = charCursor + offset
+  const endCharIndex = startCharIndex + size
+
+  if (startCharIndex < 0 || endCharIndex > chars.length || startCharIndex >= endCharIndex) {
+    return
+  }
+
+  let startJsIndex = 0
+  for (let i = 0; i < startCharIndex; i++) {
+    startJsIndex += chars[i].length
+  }
+  let endJsIndex = startJsIndex
+  for (let i = startCharIndex; i < endCharIndex; i++) {
+    endJsIndex += chars[i].length
+  }
+
+  input.setRangeText('', startJsIndex, endJsIndex, 'end')
+  input.dispatchEvent(new Event('change'))
+  input.dispatchEvent(new Event('input'))
+  onTextChange(input.value)
+}
diff --git a/page/index.ts b/page/index.ts
index 81fc6f9..76a462a 100644
--- a/page/index.ts
+++ b/page/index.ts
@@ -2,7 +2,7 @@ import type { Input } from './focus'
 import UZIP from 'uzip'
 import { activateMenuAction, getMenuActions } from './action'
 import { cli } from './cli'
-import { commit, placePanel, setPreedit } from './client'
+import { commit, deleteSurroundingText, placePanel, setPreedit } from './client'
 import { getAddons, getConfig, setConfig } from './config'
 import { OPTIONS, SERVICE_WORKER, WEB, WEB_WORKER } from './constant'
 import { hasTouch, isFirefox } from './context'
@@ -72,6 +72,7 @@ globalThis.fcitx = Object.assign((...args: any[]) => {
   invoke: (name: string, args: string) => fcitx[name](...JSON.parse(args)),
   setPreedit,
   commit,
+  deleteSurroundingText,
   sendEventToKeyboard,
   getLanguageName,
   setCurrentInputMethod,
diff --git a/wasmfrontend/wasmfrontend.cpp b/wasmfrontend/wasmfrontend.cpp
index 4749d3a..2436be0 100644
--- a/wasmfrontend/wasmfrontend.cpp
+++ b/wasmfrontend/wasmfrontend.cpp
@@ -60,6 +60,11 @@ WasmInputContext::WasmInputContext(WasmFrontend *frontend,
 
 WasmInputContext::~WasmInputContext() { destroy(); }
 
+void WasmInputContext::deleteSurroundingTextImpl(int offset,
+                                                 unsigned int size) {
+    EM_ASM(fcitx.deleteSurroundingText($0, $1), offset, size);
+}
+
 void WasmInputContext::commitStringImpl(const std::string &text) {
     EM_ASM(fcitx.commit(UTF8ToString($0)), text.c_str());
 }
diff --git a/wasmfrontend/wasmfrontend.h b/wasmfrontend/wasmfrontend.h
index e9d2752..5559cb4 100644
--- a/wasmfrontend/wasmfrontend.h
+++ b/wasmfrontend/wasmfrontend.h
@@ -51,7 +51,7 @@ class WasmInputContext : public InputContext {
 
     const char *frontend() const override { return "wasm"; }
     void commitStringImpl(const std::string &text) override;
-    void deleteSurroundingTextImpl(int offset, unsigned int size) override {}
+    void deleteSurroundingTextImpl(int offset, unsigned int size) override;
     void forwardKeyImpl(const ForwardKeyEvent &key) override {}
     void updatePreeditImpl() override;