add front end code (#27)

web/reducer.js

@@ -0,0 +1,27 @@
+import React, { useReducer } from 'react'
+const CHANGE_LOCALE = 'CHANGE_LOCALE'
+
+const mainContext = React.createContext()
+
+const reducer = (state, action) => {
+    switch (action.type) {
+        case CHANGE_LOCALE:
+            return { ...state, locale: action.locale || 'zh' }
+        default:
+            return state
+    }
+}
+
+const ContextProvider = (props) => {
+    const [state, dispatch] = useReducer(reducer, {
+        locale: 'zh'
+    })
+    return (
+        <mainContext.Provider value={{ state, dispatch }}>
+            {props.children}
+        </mainContext.Provider>
+    )
+}
+
+export { reducer, mainContext, ContextProvider }
+