meta-reducer.ts

export function productSync(reducer: ActionReducer<{ product: ProductState }>) {
  return (state, action) => {
    let reducedState = reducer(state, action);
    if (action.type === INIT) {
      const data = window.localStorage.getItem('productData');
      if (data) {
        reducedState = {
          ...reducedState,
          product: JSON.parse(data),
        };
      }
    } else if (action.type !== UPDATE) {
      window.localStorage.setItem(
        'productData',
        JSON.stringify(reducedState.product)
      );
    }
    return reducedState;
  };
}

@NgModule({
  imports: [
    StoreModule.forRoot(
      { product: productReducer },
      { metaReducers: [productSync] }
    ),
  ],
})
export class SomeModule {}