I have my ClockBlock component where I lifted state keeped in object "timer":
class ClockBlock extends Component {
constructor(props){
super(props);
this.state = { timer: props.timer }; // timer from Redux store
}
render(){
return(
<div className="clockBlock">
<Circle timer={this.state.timer} updateTimer={this.updateTimer.bind(this)} />
<Clock timer={this.state.timer} updateTimer={this.updateTimer.bind(this)} />
<ClockTerms updateTimer={this.updateTimer.bind(this)} />
</div>
)
}
All the three nested component influence each other via updateTimer function. (except ClockTerms component - it works in one direction). The function is here:
updateTimer(newDuration){
const newState = Object.assign( {}, this.state );
newState.timer.duration = newDuration;
this.setState( newState );
}
So, the problem - when I change timer using ClockTerms component I see changes in the Clock component too (via props, apparently). In the same time in the Circle component in shouldComponentUpdate function i'm trying to see the difference between the old props and the new. Here is this function:
shouldComponentUpdate(nextProps, nextState){
console.log( this.state.timer );
console.log( nextState.timer );
console.log( this.props.timer );
console.log( nextProps.timer );
return true;
}
All the console.log() calls print the same data - new props. Why? And how can I get old props?
PS: i simplified my code above, removing irrelevant from my point of view calculations. Can give whole code, if it is important.
I also use Redux here, but it seems to me it isn't engaged here much.
Great thanks in advance!
UPDATE: I also get the same picture when place the same shouldComponentUpdate function in ClockBlock (parent) component;
You can functionally set state. Because setState is async, when multiple things call setState React uses the most recent properties passed to setState.
Instead you can update state by passing an updater function. This batches all the state updates. When Reacts lifecycle begins to update state it'll process all the pending updater functions in sequence.
This is from the docs describing what happens when setState uses an object.
Subsequent calls will override values from previous calls in the same
cycle, so the quantity will only be incremented once. If the next
state depends on the current state, we recommend using the updater
function form, instead:
this.setState((state) => {
return {quantity: state.quantity + 1};
});
https://reactjs.org/docs/react-component.html#setstate
I've solved a similar situation by comparing this.state to nextProps and updating state. I don't think it's a great solution, but didn't come up with anything else jet.
state = {
dayOff: this.props.myProperty
}
shouldComponentUpdate(nextProps, nextState) {
const shouldUpdate = this.state.myProperty !== nextProps.myProperty;
if (shouldUpdate) this.state.myProperty = nextProps.myProperty
return shouldUpdate;
}
The point is that updateTimer fires BEFORE shouldComponentUpdate runs. That's it. So, when you update your lifted state in the parent component from children components (via passed in props function), keep in mind that shouldComponentUpdate will get already changed state and props.
My React component sets a state property called userInGroup based on props.
this.state = {
userInGroup: this.props.user
? this.props.user.groups.includes(props.group._id)
: false,
};
This works but does not update when the props change and the value of userInGroup should also change, until I refresh the page. How can I make this update reactively?
Maybe I could use componentWillUpdate or componentDidUpdate but then Id be repeating the logic used by userInGroup. Is this repetition inevitable?
You need to use getDerivedStateFromProps. The other methods are now deprecated and deemed unsafe.
getDerivedStateFromProps is invoked right before calling the render method, both on the initial mount and on subsequent updates. It should return an object to update the state, or null to update nothing.
This method exists for rare use cases where the state depends on changes in props over time. For example, it might be handy for implementing a component that compares its previous and next children to decide which of them to animate in and out.
static getDerivedStateFromProps(props) {
return {
userInGroup: props.user
? props.user.groups.includes(props.group._id)
: false,
}
}
Yes you need to make use of componentWillReceiveProps along with constructor/componentDidMount, when you want to update state when props change since constructor/componentDidMount are called only once when the component mounts, and componentWillReceiveProps() is invoked before a mounted component receives new props or the Parent component updates
You could write a function that contains the logic
this.state = {
userInGroup: this.getUserStatus();
};
componentWillReceiveProps(nextProps) {
if(nextProps.user !== this.props.user) {
this.setState({userInGroup: this.getUserStatus(nextProps)})
}
}
getUserStatus = (newProps) => {
const data = newProps || this.props
return data.user
? data.user.groups.includes(data.group._id)
: false
}
I am new to React, and am storing information needed only by my component in the component's state. I am running into a problem with the asynchronous nature of the this.setState call.
I have made my way around this by just assigning the state value directly, with this.state.stateKey = newValue. See below for a specific short sample case that demonstrates how this.setState does not work for me and the direct assignment does.
import React from 'react';
export default class Test extends React.Component {
constructor(props) {
super(props);
this.state = {
testVal : "Enter new text here"
}
}
runTest = (evt) => {
// if I run the test with the below line, the value
// in state is not updated before the console.log
this.setState({testVal: evt.target.value});
// if I run the test with the below line, the value
// in state is loaded before the console.log call,
// and I do get a print of the new value
this.state.testVal = evt.target.value;
console.log("testVal: ", this.state.testVal);
}
render = () => {
return(
<div>
Test
<input
class="form-control"
type="text"
defaultValue={this.state.testVal}
onBlur={this.runTest}
/>
</div>
)
}
}
My question is there anything wrong with updating state with direct assignment using this.state.stateKey = newValue? I see other workarounds, but no mention of this. And it seems so simple that there must be something wrong with it. Thanks.
Creating an immutable clone of state is a good idea because of the way state changes are compared in order to optimise rendering.
In lifecycle methods like shouldComponentUpdate, nextProps are passed in and can be compared to this.props.
If you mutate the state directly, then nextProps.someprop and this.props.someprop will always be the same and therefore you might not get the expected behaviour.
The React doc also says
NEVER mutate this.state directly, as calling setState() afterwards may replace the mutation you made. Treat this.state as if it were immutable.
I'm attempting to make a nice ApiWrapper component to populate data in various child components. From everything I've read, this should work: https://jsfiddle.net/vinniejames/m1mesp6z/1/
class ApiWrapper extends React.Component {
constructor(props) {
super(props);
this.state = {
response: {
"title": 'nothing fetched yet'
}
};
}
componentDidMount() {
this._makeApiCall(this.props.endpoint);
}
_makeApiCall(endpoint) {
fetch(endpoint).then(function(response) {
this.setState({
response: response
});
}.bind(this))
}
render() {
return <Child data = {
this.state.response
}
/>;
}
}
class Child extends React.Component {
constructor(props) {
super(props);
this.state = {
data: props.data
};
}
render() {
console.log(this.state.data, 'new data');
return ( < span > {
this.state.data.title
} < /span>);
};
}
var element = < ApiWrapper endpoint = "https://jsonplaceholder.typicode.com/posts/1" / > ;
ReactDOM.render(
element,
document.getElementById('container')
);
But for some reason, it seems the child component is not updating when the parent state changes.
Am I missing something here?
There are two issues with your code.
Your child component's initial state is set from props.
this.state = {
data: props.data
};
Quoting from this SO Answer:
Passing the intial state to a component as a prop is an anti-pattern
because the getInitialState (in our case the constuctor) method is only called the first time the
component renders. Never more. Meaning that, if you re-render that
component passing a different value as a prop, the component
will not react accordingly, because the component will keep the state
from the first time it was rendered. It's very error prone.
So if you can't avoid such a situation the ideal solution is to use the method componentWillReceiveProps to listen for new props.
Adding the below code to your child component will solve your problem with Child component re-rendering.
componentWillReceiveProps(nextProps) {
this.setState({ data: nextProps.data });
}
The second issue is with the fetch.
_makeApiCall(endpoint) {
fetch(endpoint)
.then((response) => response.json()) // ----> you missed this part
.then((response) => this.setState({ response }));
}
And here is a working fiddle: https://jsfiddle.net/o8b04mLy/
If the above solution has still not solved your problem I'll suggest you see once how you're changing the state, if you're not returning a new object then sometimes react sees no difference in the new previous and the changed state, it's a good practice to always pass a new object when changing the state, seeing the new object react will definitely re-render all the components needing that have access to that changed state.
For example: -
Here I'll change one property of an array of objects in my state, look at how I spread all the data in a new object. Also, the code below might look a bit alien to you, it's a redux reducer function BUT don't worry it's just a method to change the state.
export const addItemToCart = (cartItems,cartItemToBeAdded) => {
return cartItems.map(item => {
if(item.id===existingItem.id){
++item.quantity;
}
// I can simply return item but instead I spread the item and return a new object
return {...item}
})
}
Just make sure you're changing the state with a new object, even if you make a minor change in the state just spread it in a new object and then return, this will trigger rendering in all the appropriate places.
Hope this helped. Let me know if I'm wrong somewhere :)
There are some things you need to change.
When fetch get the response, it is not a json.
I was looking for how can I get this json and I discovered this link.
By the other side, you need to think that constructor function is called only once.
So, you need to change the way that you retrieve the data in <Child> component.
Here, I left an example code: https://jsfiddle.net/emq1ztqj/
I hope that helps.
Accepted answer and componentWillReceiveProps
The componentWillReceiveProps call in accepted answer is deprecated and will be removed from React with version 17 React Docs: UNSAFE_componentWillReceiveProps()
Using derived state logic in React
As the React docs is pointing, using derived state (meaning: a component reflecting a change that is happened in its props) can make your components harder to think, and could be an anti-pattern. React Docs: You Probably Don't Need Derived State
Current solution: getDerivedStateFromProps
If you choose to use derived state, current solution is using getDerivedStateFromProps call as #DiogoSanto said.
getDerivedStateFromProps is invoked right before calling the render method, both on the initial mount and on subsequent updates. It should return an object to update the state, or null to update nothing. React Docs: static getDerivedStateFromProps()
How to use componentWillReceiveProps
This method can not access instance properties. All it does describing React how to compute new state from a given props. Whenever props are changed, React will call this method and will use the object returned by this method as the new state.
class Child extends React.Component {
constructor() {
super(props);
// nothing changed, assign the state for the
// first time to teach its initial shape.
// (it will work without this, but will throw
// a warning)
this.state = {
data: props.data
};
}
componentWillReceiveProps(props) {
// return the new state as object, do not call .setState()
return {
data: props.data
};
}
render() {
// nothing changed, will be called after
// componentWillReceiveProps returned the new state,
// each time props are updated.
return (
<span>{this.state.data.title}</span>
);
}
}
Caution
Re-rendering a component according to a change happened in parent component can be annoying for user because of losing the user input on that component.
Derived state logic can make components harder to understand, think on. Use wisely.
I have an external (to the component), observable object that I want to listen for changes on. When the object is updated it emits change events, and then I want to rerender the component when any change is detected.
With a top-level React.render this has been possible, but within a component it doesn't work (which makes some sense since the render method just returns an object).
Here's a code example:
export default class MyComponent extends React.Component {
handleButtonClick() {
this.render();
}
render() {
return (
<div>
{Math.random()}
<button onClick={this.handleButtonClick.bind(this)}>
Click me
</button>
</div>
)
}
}
Clicking the button internally calls this.render(), but that's not what actually causes the rendering to happen (you can see this in action because the text created by {Math.random()} doesn't change). However, if I simply call this.setState() instead of this.render(), it works fine.
So I guess my question is: do React components need to have state in order to rerender? Is there a way to force the component to update on demand without changing the state?
In class components, you can call this.forceUpdate() to force a rerender.
Documentation: https://facebook.github.io/react/docs/component-api.html
In function components, there's no equivalent of forceUpdate, but you can contrive a way to force updates with the useState hook.
forceUpdate should be avoided because it deviates from a React mindset. The React docs cite an example of when forceUpdate might be used:
By default, when your component's state or props change, your component will re-render. However, if these change implicitly (eg: data deep within an object changes without changing the object itself) or if your render() method depends on some other data, you can tell React that it needs to re-run render() by calling forceUpdate().
However, I'd like to propose the idea that even with deeply nested objects, forceUpdate is unnecessary. By using an immutable data source tracking changes becomes cheap; a change will always result in a new object so we only need to check if the reference to the object has changed. You can use the library Immutable JS to implement immutable data objects into your app.
Normally you should try to avoid all uses of forceUpdate() and only read from this.props and this.state in render(). This makes your component "pure" and your application much simpler and more efficient.forceUpdate()
Changing the key of the element you want re-rendered will work. Set the key prop on your element via state and then when you want to update set state to have a new key.
<Element key={this.state.key} />
Then a change occurs and you reset the key
this.setState({ key: Math.random() });
I want to note that this will replace the element that the key is changing on. An example of where this could be useful is when you have a file input field that you would like to reset after an image upload.
While the true answer to the OP's question would be forceUpdate() I have found this solution helpful in different situations. I also want to note that if you find yourself using forceUpdate you may want to review your code and see if there is another way to do things.
NOTE 1-9-2019:
The above (changing the key) will completely replace the element. If you find yourself updating the key to make changes happen you probably have an issue somewhere else in your code. Using Math.random() in key will re-create the element with each render. I would NOT recommend updating the key like this as react uses the key to determine the best way to re-render things.
In 2021 and 2022, this is the official way to forceUpdate a React Functional Component.
const [, forceUpdate] = useReducer(x => x + 1, 0);
function handleClick() {
forceUpdate();
}
I know the OP is for a class component. But the question was asked in 2015 and now that hooks are available, many may search for forceUpdate in functional components. This little bit is for them.
Edit 18th Apr 2022
It's usually bad practice to force update your components.
A few reasons that can cause the need to use force updates.
Not using state variables where you have to - local, redux, context.
The field from the state object you are trying to access and expecting to update/change is too deeply nested in objects or arrays. Even Redux advises to maintain flat objects or arrays. If only one field value changes in a complex object, React may not figure out that the state object has changed, thus it does not update the component. Keep your state flat and simple.
The key on your list items, as mentioned in another answer. In fact, this can cause other unexpected behaviors as well. I've seen lists where items are repeatedly rendered (duplicates) because the keys aren't identical or the keys are just missing altogether. Always request the backend team to send unique ids everywhere possible! Avoid using array indexes for keys. Do not try to create unique ids on the front-end by using nanoid, uuid or random. Because ids created using above methods change each time the component updates (keys provided to a list need to be static and the same on each render). Creating unique ids is usually a backend concern. Try your best to not bring that requirement to the front-end. The front-end's responsibility is only to paint what data the backend returns and not create data on the fly.
If your useEffect, useCallback dependency arrays do not have the proper values set. Use ESLint to help you with this one! Also, this is one of the biggest causes for memory leaks in React. Clean up your state and event listeners in the return callback to avoid memory leaks. Because such memory leaks are awfully difficult to debug.
Always keep an eye on the console. It's your best friend at work. Solving warning and errors that show up in the console can fix a whole lot of nasty things - bugs and issues that you aren't even aware off.
A few things I can remember that I did wrong. In case it helps..
Actually, forceUpdate() is the only correct solution as setState() might not trigger a re-render if additional logic is implemented in shouldComponentUpdate() or when it simply returns false.
forceUpdate()
Calling forceUpdate() will cause render() to be called on the component, skipping shouldComponentUpdate(). more...
setState()
setState() will always trigger a re-render unless conditional rendering logic is implemented in shouldComponentUpdate(). more...
forceUpdate() can be called from within your component by this.forceUpdate()
Hooks: How can I force component to re-render with hooks in React?
BTW: Are you mutating state or your nested properties don't propagate?
How to update nested state properties in React
Sandbox
I Avoided forceUpdate by doing following
WRONG WAY : do not use index as key
this.state.rows.map((item, index) =>
<MyComponent cell={item} key={index} />
)
CORRECT WAY : Use data id as key, it can be some guid etc
this.state.rows.map((item) =>
<MyComponent item={item} key={item.id} />
)
so by doing such code improvement your component will be UNIQUE and render naturally
When you want two React components to communicate, which are not bound by a relationship (parent-child), it is advisable to use Flux or similar architectures.
What you want to do is to listen for changes of the observable component store, which holds the model and its interface, and saving the data that causes the render to change as state in MyComponent. When the store pushes the new data, you change the state of your component, which automatically triggers the render.
Normally you should try to avoid using forceUpdate() . From the documentation:
Normally you should try to avoid all uses of forceUpdate() and only read from this.props and this.state in render(). This makes your application much simpler and more efficient
use hooks or HOC take your pick
Using hooks or the HOC (higher order component) pattern, you can have automatic updates when your stores change. This is a very light-weight approach without a framework.
useStore Hooks way to handle store updates
interface ISimpleStore {
on: (ev: string, fn: () => void) => void;
off: (ev: string, fn: () => void) => void;
}
export default function useStore<T extends ISimpleStore>(store: T) {
const [storeState, setStoreState] = useState({store});
useEffect(() => {
const onChange = () => {
setStoreState({store});
}
store.on('change', onChange);
return () => {
store.off('change', onChange);
}
}, []);
return storeState.store;
}
withStores HOC handle store updates
export default function (...stores: SimpleStore[]) {
return function (WrappedComponent: React.ComponentType<any>) {
return class WithStore extends PureComponent<{}, {lastUpdated: number}> {
constructor(props: React.ComponentProps<any>) {
super(props);
this.state = {
lastUpdated: Date.now(),
};
this.stores = stores;
}
private stores?: SimpleStore[];
private onChange = () => {
this.setState({lastUpdated: Date.now()});
};
componentDidMount = () => {
this.stores &&
this.stores.forEach((store) => {
// each store has a common change event to subscribe to
store.on('change', this.onChange);
});
};
componentWillUnmount = () => {
this.stores &&
this.stores.forEach((store) => {
store.off('change', this.onChange);
});
};
render() {
return (
<WrappedComponent
lastUpdated={this.state.lastUpdated}
{...this.props}
/>
);
}
};
};
}
SimpleStore class
import AsyncStorage from '#react-native-community/async-storage';
import ee, {Emitter} from 'event-emitter';
interface SimpleStoreArgs {
key?: string;
defaultState?: {[key: string]: any};
}
export default class SimpleStore {
constructor({key, defaultState}: SimpleStoreArgs) {
if (key) {
this.key = key;
// hydrate here if you want w/ localState or AsyncStorage
}
if (defaultState) {
this._state = {...defaultState, loaded: false};
} else {
this._state = {loaded: true};
}
}
protected key: string = '';
protected _state: {[key: string]: any} = {};
protected eventEmitter: Emitter = ee({});
public setState(newState: {[key: string]: any}) {
this._state = {...this._state, ...newState};
this.eventEmitter.emit('change');
if (this.key) {
// store on client w/ localState or AsyncStorage
}
}
public get state() {
return this._state;
}
public on(ev: string, fn:() => void) {
this.eventEmitter.on(ev, fn);
}
public off(ev: string, fn:() => void) {
this.eventEmitter.off(ev, fn);
}
public get loaded(): boolean {
return !!this._state.loaded;
}
}
How to Use
In the case of hooks:
// use inside function like so
const someState = useStore(myStore);
someState.myProp = 'something';
In the case of HOC:
// inside your code get/set your store and stuff just updates
const val = myStore.myProp;
myOtherStore.myProp = 'something';
// return your wrapped component like so
export default withStores(myStore)(MyComponent);
MAKE SURE
To export your stores as a singleton to get the benefit of global change like so:
class MyStore extends SimpleStore {
public get someProp() {
return this._state.someProp || '';
}
public set someProp(value: string) {
this.setState({...this._state, someProp: value});
}
}
// this is a singleton
const myStore = new MyStore();
export {myStore};
This approach is pretty simple and works for me. I also work in large teams and use Redux and MobX and find those to be good as well but just a lot of boilerplate. I just personally like my own approach because I always hated a lot of code for something that can be simple when you need it to be.
So I guess my question is: do React components need to have state in
order to rerender? Is there a way to force the component to update on
demand without changing the state?
The other answers have tried to illustrate how you could, but the point is that you shouldn't. Even the hacky solution of changing the key misses the point. The power of React is giving up control of manually managing when something should render, and instead just concerning yourself with how something should map on inputs. Then supply stream of inputs.
If you need to manually force re-render, you're almost certainly not doing something right.
There are a few ways to rerender your component:
The simplest solution is to use forceUpdate() method:
this.forceUpdate()
One more solution is to create not used key in the state(nonUsedKey)
and call setState function with update of this nonUsedKey:
this.setState({ nonUsedKey: Date.now() } );
Or rewrite all current state:
this.setState(this.state);
Props changing also provides component rerender.
For completeness, you can also achieve this in functional components:
const [, updateState] = useState();
const forceUpdate = useCallback(() => updateState({}), []);
// ...
forceUpdate();
Or, as a reusable hook:
const useForceUpdate = () => {
const [, updateState] = useState();
return useCallback(() => updateState({}), []);
}
// const forceUpdate = useForceUpdate();
See: https://stackoverflow.com/a/53215514/2692307
Please note that using a force-update mechanism is still bad practice as it goes against the react mentality, so it should still be avoided if possible.
You could do it a couple of ways:
1. Use the forceUpdate() method:
There are some glitches that may happen when using the forceUpdate() method. One example is that it ignores the shouldComponentUpdate() method and will re-render the view regardless of whether shouldComponentUpdate() returns false. Because of this using forceUpdate() should be avoided when at all possible.
2. Passing this.state to the setState() method
The following line of code overcomes the problem with the previous example:
this.setState(this.state);
Really all this is doing is overwriting the current state with the current state which triggers a re-rendering. This still isn't necessarily the best way to do things, but it does overcome some of the glitches you might encounter using the forceUpdate() method.
We can use this.forceUpdate() as below.
class MyComponent extends React.Component {
handleButtonClick = ()=>{
this.forceUpdate();
}
render() {
return (
<div>
{Math.random()}
<button onClick={this.handleButtonClick}>
Click me
</button>
</div>
)
}
}
ReactDOM.render(<MyComponent /> , mountNode);
The Element 'Math.random' part in the DOM only gets updated even if you use the setState to re-render the component.
All the answers here are correct supplementing the question for understanding..as we know to re-render a component with out using setState({}) is by using the forceUpdate().
The above code runs with setState as below.
class MyComponent extends React.Component {
handleButtonClick = ()=>{
this.setState({ });
}
render() {
return (
<div>
{Math.random()}
<button onClick={this.handleButtonClick}>
Click me
</button>
</div>
)
}
}
ReactDOM.render(<MyComponent /> , mountNode);
Just another reply to back-up the accepted answer :-)
React discourages the use of forceUpdate() because they generally have a very "this is the only way of doing it" approach toward functional programming. This is fine in many cases, but many React developers come with an OO-background, and with that approach, it's perfectly OK to listen to an observable object.
And if you do, you probably know you MUST re-render when the observable "fires", and as so, you SHOULD use forceUpdate() and it's actually a plus that shouldComponentUpdate() is NOT involved here.
Tools like MobX, that takes an OO-approach, is actually doing this underneath the surface (actually MobX calls render() directly)
forceUpdate(), but every time I've ever heard someone talk about it, it's been followed up with you should never use this.
forceUpdate(); method will work but it is advisable to use setState();
In order to accomplish what you are describing please try this.forceUpdate().
Another way is calling setState, AND preserve state:
this.setState(prevState=>({...prevState}));
I have found it best to avoid forceUpdate(). One way to force re-render is to add dependency of render() on a temporary external variable and change the value of that variable as and when needed.
Here's a code example:
class Example extends Component{
constructor(props){
this.state = {temp:0};
this.forceChange = this.forceChange.bind(this);
}
forceChange(){
this.setState(prevState => ({
temp: prevState.temp++
}));
}
render(){
return(
<div>{this.state.temp &&
<div>
... add code here ...
</div>}
</div>
)
}
}
Call this.forceChange() when you need to force re-render.
ES6 - I am including an example, which was helpful for me:
In a "short if statement" you can pass empty function like this:
isReady ? ()=>{} : onClick
This seems to be the shortest approach.
()=>{}
use useEffect as a mix of componentDidMount, componentDidUpdate, and componentWillUnmount, as stated in the React documentation.
To behave like componentDidMount, you would need to set your useEffect like this:
useEffect(() => console.log('mounted'), []);
The first argument is a callback that will be fired based on the second argument, which is an array of values. If any of the values in that second argument changed, the callback function you defined inside your useEffect will be fired.
In the example I'm showing, however, I'm passing an empty array as my second argument, and that will never be changed, so the callback function will be called once when the component mounts.
That kind of summarizes useEffect. If instead of an empty value, you have an argument, like:
useEffect(() => {
}, [props.lang]);
That means that every time props.lang changes, your callback function will be called. The useEffect will not rerender your component really, unless you're managing some state inside that callback function that could fire a re-render.
If you want to fire a re-render, your render function needs to have a state that you are updating in your useEffect.
For example, in here, the render function starts by showing English as the default language and in my use effect I change that language after 3 seconds, so the render is re-rendered and starts showing "spanish".
function App() {
const [lang, setLang] = useState("english");
useEffect(() => {
setTimeout(() => {
setLang("spanish");
}, 3000);
}, []);
return (
<div className="App">
<h1>Lang:</h1>
<p>{lang}</p>
</div>
);
}
You can use forceUpdate() for more details check (forceUpdate()).