Considering below hooks example
import { useState } from 'react';
function Example() {
const [count, setCount] = useState(0);
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}
Basically we use this.forceUpdate() method to force the component to re-render immediately in React class components like below example
class Test extends Component{
constructor(props){
super(props);
this.state = {
count:0,
count2: 100
}
this.setCount = this.setCount.bind(this);//how can I do this with hooks in functional component
}
setCount(){
let count = this.state.count;
count = count+1;
let count2 = this.state.count2;
count2 = count2+1;
this.setState({count});
this.forceUpdate();
//before below setState the component will re-render immediately when this.forceUpdate() is called
this.setState({count2: count
}
render(){
return (<div>
<span>Count: {this.state.count}></span>.
<button onClick={this.setCount}></button>
</div>
}
}
But my query is How can I force above functional component to re-render immediately with hooks?
This question is related to
javascript
reactjs
react-native
react-hooks
This is possible with useState
or useReducer
, since useState
uses useReducer
internally:
const [, updateState] = React.useState();
const forceUpdate = React.useCallback(() => updateState({}), []);
forceUpdate
isn't intended to be used under normal circumstances, only in testing or other outstanding cases. This situation may be addressed in a more conventional way.
setCount
is an example of improperly used forceUpdate
, setState
is asynchronous for performance reasons and shouldn't be forced to be synchronous just because state updates weren't performed correctly. If a state relies on previously set state, this should be done with updater function,
If you need to set the state based on the previous state, read about the updater argument below.
<...>
Both state and props received by the updater function are guaranteed to be up-to-date. The output of the updater is shallowly merged with state.
setCount
may not be an illustrative example because its purpose is unclear but this is the case for updater function:
setCount(){
this.setState(({count}) => ({ count: count + 1 }));
this.setState(({count2}) => ({ count2: count + 1 }));
this.setState(({count}) => ({ count2: count + 1 }));
}
This is translated 1:1 to hooks, with the exception that functions that are used as callbacks should better be memoized:
const [state, setState] = useState({ count: 0, count2: 100 });
const setCount = useCallback(() => {
setState(({count}) => ({ count: count + 1 }));
setState(({count2}) => ({ count2: count + 1 }));
setState(({count}) => ({ count2: count + 1 }));
}, []);
As the others have mentioned, useState
works - here is how mobx-react-lite implements updates - you could do something similar.
Define a new hook, useForceUpdate
-
import { useState, useCallback } from 'react'
export function useForceUpdate() {
const [, setTick] = useState(0);
const update = useCallback(() => {
setTick(tick => tick + 1);
}, [])
return update;
}
and use it in a component -
const forceUpdate = useForceUpdate();
if (...) {
forceUpdate(); // force re-render
}
See https://github.com/mobxjs/mobx-react-lite/blob/master/src/utils.ts and https://github.com/mobxjs/mobx-react-lite/blob/master/src/useObserver.ts
Generally, you can use any state handling approach you want to trigger an update.
const forceUpdate: () => void = React.useState()[1].bind(null, {}) // see NOTE below
const forceUpdate = React.useReducer(() => ({}), {})[1] as () => void
Just wrap whatever approach you prefer like this
function useForceUpdate(): () => void {
return React.useReducer(() => ({}), {})[1] as () => void // <- paste here
}
"To trigger an update" means to tell React engine that some value has changed and that it should rerender your component.
[, setState]
from useState()
requires a parameter. We get rid of it by binding a fresh object {}
.
() => ({})
in useReducer
is a dummy reducer that returns a fresh object each time an action is dispatched.
{}
(fresh object) is required so that it triggers an update by changing a reference in the state.
PS: useState
just wraps useReducer
internally. source
NOTE: Using .bind with useState causes a change in function reference between renders. It is possible to wrap it inside useCallback as already explained here, but then it wouldn't be a sexy one-linerâ„¢. The Reducer version already keeps reference equality between renders. This is important if you want to pass the forceUpdate function in props.
const forceUpdate = React.useState()[1].bind(null, {}) // see NOTE above
const forceUpdate = React.useReducer(() => ({}))[1]
Alternative to @MinhKha's answer:
It can be much cleaner with useReducer
:
const [, forceUpdate] = useReducer(x => x + 1, 0);
Usage:
forceUpdate()
- cleaner without params
React Hooks FAQ official solution for forceUpdate
:
const [_, forceUpdate] = useReducer((x) => x + 1, 0);
// usage
<button onClick={forceUpdate}>Force update</button>
const App = () => {
const [_, forceUpdate] = useReducer((x) => x + 1, 0);
return (
<div>
<button onClick={forceUpdate}>Force update</button>
<p>Forced update {_} times</p>
</div>
);
};
ReactDOM.render(<App />, document.getElementById("root"));
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.10.1/umd/react.production.min.js" integrity="sha256-vMEjoeSlzpWvres5mDlxmSKxx6jAmDNY4zCt712YCI0=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.10.1/umd/react-dom.production.min.js" integrity="sha256-QQt6MpTdAD0DiPLhqhzVyPs1flIdstR4/R7x4GqCvZ4=" crossorigin="anonymous"></script>
<script>var useReducer = React.useReducer</script>
<div id="root"></div>
_x000D_
You can simply define the useState like that:
const [, forceUpdate] = React.useState(0);
And usage: forceUpdate(n => !n)
Hope this help !
You should preferably only have your component depend on state and props and it will work as expected, but if you really need a function to force the component to re-render, you could use the useState
hook and call the function when needed.
Example
const { useState, useEffect } = React;_x000D_
_x000D_
function Foo() {_x000D_
const [, forceUpdate] = useState();_x000D_
_x000D_
useEffect(() => {_x000D_
setTimeout(forceUpdate, 2000);_x000D_
}, []);_x000D_
_x000D_
return <div>{Date.now()}</div>;_x000D_
}_x000D_
_x000D_
ReactDOM.render(<Foo />, document.getElementById("root"));
_x000D_
<script src="https://unpkg.com/[email protected]/umd/react.production.min.js"></script>_x000D_
<script src="https://unpkg.com/[email protected]/umd/react-dom.production.min.js"></script>_x000D_
_x000D_
<div id="root"></div>
_x000D_
Simple code
const forceUpdate = React.useReducer(bool => !bool)[1];
Use:
forceUpdate();
Potential option is to force update only on specific component using key
. Updating the key trigger a rendering of the component (which failed to update before)
For example:
const [tableKey, setTableKey] = useState(1);
...
useEffect(() => {
...
setTableKey(tableKey + 1);
}, [tableData]);
...
<DataTable
key={tableKey}
data={tableData}/>
You can (ab)use normal hooks to force a rerender by taking advantage of the fact that React doesn't print booleans in JSX code
// create a hook
const [forceRerender, setForceRerender] = React.useState(true);
// ...put this line where you want to force a rerender
setForceRerender(!forceRerender);
// ...make sure that {forceRerender} is "visible" in your js code
// ({forceRerender} will not actually be visible since booleans are
// not printed, but updating its value will nonetheless force a
// rerender)
return (
<div>{forceRerender}</div>
)
Solution in one single line:
const [,forceRender] = useReducer((s) => s+1, 0)
You can learn about useReducer here. https://reactjs.org/docs/hooks-reference.html#usereducer
One line solution:
const useForceUpdate = () => useState()[1];
useState returns a pair of values: the current state and a function that updates it - state and setter, here we are using only the setter in order to force re-render.
This will render depending components 3 times (arrays with equal elements aren't equal):
const [msg, setMsg] = useState([""])
setMsg(["test"])
setMsg(["test"])
setMsg(["test"])
My variation of forceUpdate
is not via a counter
but rather via an object:
// Emulates `forceUpdate()`
const [unusedState, setUnusedState] = useState()
const forceUpdate = useCallback(() => setUnusedState({}), [])
Because {} !== {}
every time.
react-tidy
has a custom hook just for doing that called useRefresh
:
import React from 'react'
import {useRefresh} from 'react-tidy'
function App() {
const refresh = useRefresh()
return (
<p>
The time is {new Date()} <button onClick={refresh}>Refresh</button>
</p>
)
}
Disclaimer I am the writer of this library.
For regular React Class based components, refer to React Docs for the forceUpdate
api at this URL. The docs mention that:
Normally you should try to avoid all uses of forceUpdate() and only read from this.props and this.state in render()
However, it is also mentioned in the docs that:
If your render() method depends on some other data, you can tell React that the component needs re-rendering by calling forceUpdate().
So, although use cases for using forceUpdate
might be rare, and I have not used it ever, however I have seen it used by other developers in some legacy corporate projects that I have worked on.
So, for the equivalent functionality for Functional Components, refer to the React Docs for HOOKS at this URL. Per the above URL, one can use the "useReducer" hook to provide a forceUpdate
functionality for Functional Components.
A working code sample that does not use state or props
is provided below, which is also available on CodeSandbox at this URL
import React, { useReducer, useRef } from "react";
import ReactDOM from "react-dom";
import "./styles.css";
function App() {
// Use the useRef hook to store a mutable value inside a functional component for the counter
let countref = useRef(0);
const [, forceUpdate] = useReducer(x => x + 1, 0);
function handleClick() {
countref.current++;
console.log("Count = ", countref.current);
forceUpdate(); // If you comment this out, the date and count in the screen will not be updated
}
return (
<div className="App">
<h1> {new Date().toLocaleString()} </h1>
<h2>You clicked {countref.current} times</h2>
<button
onClick={() => {
handleClick();
}}
>
ClickToUpdateDateAndCount
</button>
</div>
);
}
const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);
NOTE: An alternate approach using the useState hook (instead of useReducer) is also available at this URL.
Source: Stackoverflow.com