prevstate in usestate
const [prevState, setState] = React.useState([]);
setState(prevState => [...prevState, 'somedata'] );
prevstate in usestate
const [prevState, setState] = React.useState([]);
setState(prevState => [...prevState, 'somedata'] );
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>
</>
);
}
this.setstate prevstate
this.setState(prevState => ({ n: !prevState.n }))
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