better typing

lib/growthbook/init.ts

@@ -3,6 +3,10 @@ import { GrowthBook } from '@growthbook/growthbook-react';
 import config from 'configs/app';
 import * as mixpanel from 'lib/mixpanel';
 
+export interface GrowthBookFeatures {
+  test_value: string;
+}
+
 export const growthBook = (() => {
   const feature = config.features.growthBook;
 
@@ -10,7 +14,7 @@ export const growthBook = (() => {
     return;
   }
 
-  return new GrowthBook({
+  return new GrowthBook<GrowthBookFeatures>({
     apiHost: 'https://cdn.growthbook.io',
     clientKey: feature.clientKey,
     enableDevMode: config.app.isDev,

lib/growthbook/useFeatureValue.ts

+import type { WidenPrimitives } from '@growthbook/growthbook';
 import { useFeatureValue, useGrowthBook } from '@growthbook/growthbook-react';
 
-export default function useGbFeatureValue<T extends Parameters<typeof useFeatureValue>[1]>(
-  name: Parameters<typeof useFeatureValue>[0],
-  fallback: T,
-): { value: ReturnType<typeof useFeatureValue<T>>; isLoading: boolean } {
+import type { GrowthBookFeatures } from './init';
+
+export default function useGbFeatureValue<Name extends keyof GrowthBookFeatures>(
+  name: Name,
+  fallback: GrowthBookFeatures[Name],
+): { value: WidenPrimitives<GrowthBookFeatures[Name]>; isLoading: boolean } {
   const value = useFeatureValue(name, fallback);
   const growthBook = useGrowthBook();
 

lib/mixpanel/useInit.tsx

@@ -30,7 +30,7 @@ export default function useMixpanelInit() {
       loaded: function() {
         growthBook?.setAttributes({
           ...growthBook.getAttributes(),
-          time_zone: Intl.DateTimeFormat().resolvedOptions().timeZone,
+          timezone: Intl.DateTimeFormat().resolvedOptions().timeZone,
           language: window.navigator.language,
         });
       },