React Cache: How to Use the useMemo Hook

As you become more proficient in React programming, performance optimization becomes a crucial focus in your development process. Like any programming tool or methodology, caching plays a significant role when it comes to optimizing React applications. In React, caching typically refers to memoization, which helps improve performance by reducing the number of times a component re-renders due to state changes or prop mutations.

Default Caching Behavior in React

By default, React uses a technique called “shallow comparison” to determine whether a component should be re-rendered. Essentially, if a component’s properties or state haven’t changed, React assumes that the component’s output hasn’t changed either and won’t re-render it. While this default caching behavior is effective, it’s not always sufficient for optimizing complex components that require advanced state management.

The useMemo Hook

The useMemo hook is useful when you need to perform a costly calculation to return a value and want to ensure that the calculation only runs when necessary. By memoizing the value using useMemo, you can ensure that the value is recalculated only when its dependencies change.

Here’s an example of how to use useMemo in a React componente:


import React, { useState, useMemo } from 'react';

function Example() {
const [count, setCount] = useState(0);
const [text, setText] = useState('');

// Función de cálculo costoso
const expensiveCalculation = (num) => {
console.log('Calculando...');
let result = 0;
for (let i = 0; i < 1000000000; i++) { result += num; } return result; }; // Memoizar el resultado del cálculo costoso const memoizedValue = useMemo(() => expensiveCalculation(count), [count]);

return (

Resultado del cálculo: {memoizedValue}


setText(e.target.value)}
placeholder="Escribe algo..."
/>

);
}

export default Example;

Remember that useMemo is especially useful when you have expensive calculations or frequently executed functions in your components.