reactjs – 限制Redux仅更新受更改影响的组件

示例App

class App extends React.Component {

  render(){return (
          <div> 
            <Navbar data={this.props.navbar} />
            <Content data={this.props.content} />
          </div>);
  }

}
select (state) => ({ navbar:state.navbar,content:state.content});
export default connect(select)(App);

组件

export const NavbarForm = props => {
  console.log('RENDERING with props--->',props);
  return (<h1>NAV {props.data.val}</h1>);
};
export const ContentForm = props => {
  console.log('RENDERING CONTENT with props--->',props);
  return (<h1>CONTENT {props.data.val}</h1>);
};

////////INDEX.js//////

const placeholderReducer = (state={val:0},action)=>{
//will update val to current time if action start with test/;
if(action.type.indexOf('TEST/') === 0)return {val:Date.now();}

return state;
}

export const rootReducer = combineReducers({
  navbar:placeholderReducer,content: (state,action)=>(state || {}),//**this will never do a thing.. so content should never updates right !!**
});

const store = createStore(rootReducer,{},applyMiddleware(thunk));

render( <Provider store={store}> <App /></Provider>,document.getElementById('app')
);
setInterval(()=>{  store.dispatch(()=>{type:'TEST/BOOM'})  },3000);

好吧,在这个应用程序中,我期望Navbar组件将每3000毫秒更新一次,而内容组件永远不会更新,因为它的reducer将始终返回相同的状态.

但是我发现每次触发动作时两个组件都会执行reRender非常奇怪.

这是设计的吗？如果我的应用程序有100个组件,我应该担心性能吗？