useRef
/*
A common use case is to access a child imperatively:
*/
function TextInputWithFocusButton() {
const inputEl = useRef(null);
const onButtonClick = () => {
// `current` points to the mounted text input element
inputEl.current.focus();
};
return (
<>
<input ref={inputEl} type="text" />
<button onClick={onButtonClick}>Focus the input</button>
</>
);
}usestate hook
import React, { useState } from 'react';
function Example() {
// Declare a new state variable, which we'll call "count"
const [count, setCount] = useState(0);
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}useState hook with callback
const [state, setState] = useState(null);
const myCallbacksList = useRef([]);
const setStateWithCallback= (newState, callback) => {
setState(state);
if(callback) myCallbackList.current.push(callback)
}
useEffect(() => {
myCallbacksList.current.forEach((callback) => callback())
myCallbacksList.current = [];
}, [state]);
…
setStateWithCallback(newState, myCallback)usestate hook callback
const [counter, setCounter] = useState(0);
const doSomething = () => {
setCounter(123);
}
useEffect(() => {
console.log('Do something after counter has changed', counter);
}, [counter]);Copyright © 2021 Codeinu
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