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>
</>
);
}react memo
function MyComponent(props) {
/* render using props */
}
function areEqual(prevProps, nextProps) {
/*
return true if passing nextProps to render would return
the same result as passing prevProps to render,
otherwise return false
*/
}
export default React.memo(MyComponent, areEqual);how to use react memo hooks
function moviePropsAreEqual(prevMovie, nextMovie) {
return prevMovie.title === nextMovie.title
&& prevMovie.releaseDate === nextMovie.releaseDate;
}
const MemoizedMovie2 = React.memo(Movie, moviePropsAreEqual);react memo
/* this is for es6 onward */
/* React.memo is the new PureComponent */
import React, { memo } from 'react'
const MyComponent = () => {
return <>something</>
}
export default memo(MyComponent)how to use react memo hooks
const computeLetterCount = word => {
let i = 0;
while (i < 1000000000) i++;
return word.length;
};
// Memoize computeLetterCount so it uses cached return value if input array ...
// ... values are the same as last time the function was run.
const letterCount = useMemo(() => computeLetterCount(word), [word]);import React, { memo } from 'react';
const MyComponent = React.memo(function MyComponent(props) {
/* only rerenders if props change */
});Copyright © 2021 Codeinu
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