diff --git a/page/Fcitx5.d.ts b/page/Fcitx5.d.ts
index 264a21d..475b652 100644
--- a/page/Fcitx5.d.ts
+++ b/page/Fcitx5.d.ts
@@ -28,6 +28,7 @@ export interface FCITX {
   updateStatusArea: () => void
   getConfig: (uri: string) => Config
   setConfig: (uri: string, json: object) => void
+  jsKeyToFcitxString: (event: KeyboardEvent) => string
 }
 
 export const fcitxReady: Promise<null>
diff --git a/page/index.ts b/page/index.ts
index fa15d80..ddc95c4 100644
--- a/page/index.ts
+++ b/page/index.ts
@@ -1,6 +1,6 @@
 import Module from './module'
 import { blur, clickPanel, focus } from './focus'
-import { keyEvent } from './keycode'
+import { jsKeyToFcitxString, keyEvent } from './keycode'
 import { commit, hidePanel, placePanel, setPreedit } from './client'
 import { currentInputMethod, getAllInputMethods, getInputMethods, setCurrentInputMethod, setInputMethods } from './input-method'
 import { getConfig, setConfig } from './config'
@@ -43,6 +43,7 @@ window.fcitx = {
   getAllInputMethods,
   getConfig,
   setConfig,
+  jsKeyToFcitxString,
   enable() {
     document.addEventListener('focus', focus, true)
     document.addEventListener('blur', blur, true)
diff --git a/page/keycode.ts b/page/keycode.ts
index 8b316d7..866529a 100644
--- a/page/keycode.ts
+++ b/page/keycode.ts
@@ -1,19 +1,35 @@
 import Module from './module'
 import { getInputElement } from './focus'
 
-export function keyEvent(event: KeyboardEvent) {
-  if (!getInputElement()) {
-    return
-  }
-  const isRelease = event.type === 'keyup'
+function extract(event: KeyboardEvent): [string, string, number] | undefined {
   const { key, code, shiftKey, altKey, ctrlKey, metaKey } = event
   // Host IME
   if (key === 'Process') {
-    return
+    return undefined
   }
   const capsLock = event.getModifierState('CapsLock')
   const modifiers = Number(shiftKey) | Number(capsLock) << 1 | Number(ctrlKey) << 2 | Number(altKey) << 3 | Number(metaKey) << 6
-  if (Module.ccall('process_key', 'bool', ['string', 'string', 'number', 'bool'], [key, code, modifiers, isRelease])) {
+  return [key, code, modifiers]
+}
+
+export function keyEvent(event: KeyboardEvent) {
+  if (!getInputElement()) {
+    return
+  }
+  const extracted = extract(event)
+  if (!extracted) {
+    return
+  }
+  const isRelease = event.type === 'keyup'
+  if (Module.ccall('process_key', 'bool', ['string', 'string', 'number', 'bool'], [...extracted, isRelease])) {
     event.preventDefault()
   }
 }
+
+export function jsKeyToFcitxString(event: KeyboardEvent) {
+  const extracted = extract(event)
+  if (!extracted) {
+    return ''
+  }
+  return Module.ccall('js_key_to_fcitx_string', 'string', ['string', 'string', 'number'], extracted)
+}
diff --git a/src/keycode.cpp b/src/keycode.cpp
index 3695934..a7f987c 100644
--- a/src/keycode.cpp
+++ b/src/keycode.cpp
@@ -1,4 +1,5 @@
 #include "keycode.h"
+#include <emscripten.h>
 #include <fcitx-utils/log.h>
 
 namespace fcitx {
@@ -224,4 +225,13 @@ Key js_key_to_fcitx_key(const std::string &key, const std::string &code,
     return Key{js_key_to_fcitx_keysym(key, code), KeyStates{modifiers},
                js_keycode_to_fcitx_keycode(code)};
 }
+
+extern "C" {
+EMSCRIPTEN_KEEPALIVE const char *
+js_key_to_fcitx_string(const char *key, const char *code, uint32_t modifiers) {
+    static std::string ret;
+    ret = js_key_to_fcitx_key(key, code, modifiers).normalize().toString();
+    return ret.c_str();
+}
+}
 } // namespace fcitx