React useMemo Hook: React‘s useMemo hook is a built-in function that allows you to memoize expensive computations so that they only re-run when necessary. This can be useful in optimizing performance by avoiding unnecessary re-computations.
To use useMemo, you first need to create a function that performs the expensive computation you want to memoize. You then pass this function and an array of dependencies to the React’s useMemo function. The useMemo function will return a memoized version of the function that only re-computes when one of its dependencies changes.
Here’s an example of how you might use React’s useMemo to memoize the factorial of a number:
import React, { useState, useMemo } from 'react';
function Factorial() {
const [num, setNum] = useState(0);
const factorial = useMemo(() => {
let result = 1;
for (let i = 2; i <= num; i++) {
result *= i;
}
return result;
}, [num]);
return (
<div>
<p>Num: {num}</p>
<input value={num} onChange={(e) => setNum(parseInt(e.target.value))} />
<p>Factorial: {factorial}</p>
</div>
);
}
In this example, we first declare a state variable num and a setter function setNum using the useState hook.
We then declare a factorial function using the useMemo hook. The factorial function calculates the factorial of num using a for loop. We pass num as a dependency to useMemo so that the factorial function only re-computes when num changes.
We then render an input element that allows the user to input num, and display the factorial of num using the factorial function.
By using useMemo, we can ensure that the factorial function only re-computes when num changes. This can help optimize performance by avoiding unnecessary re-computations.
useMemo is a powerful hook that allows you to memoize expensive computations and optimize performance in functional components. By using it, you can write more efficient and performant code that is easier to understand and maintain.
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