In the world of React, when building a complex application performance optimization is a crucial aspect. Two of the most commonly used hooks that can aid in this are useCallback and useMemo. While both hooks are used to better the performance of the application, they have different use cases and can often be confused with each other. In this blog, we will take a closer look at the difference between useCallback and useMemo also when to use each one.
Pre-requisites:
Understanding of basic javascript.
Understanding of setting up react project.
What is useCallback?
useCallback is a hook that gives you the memoize function. When a function is memoized, the function instance is cached and returned whenever the dependencies specified in the second argument of useCallback do not change. It can help to avoid the unnecessary re-rendering of components that use the memoized function.
Here is an example...
In this example, we have a component MyComponent that has a count state and a memoized function handleClick. The handleClick function is memoized using useCallback because it's used as an event handler for the button click event.
By memoizing handleClick, we can avoid unnecessary re-renders of MyComponent and prevent the function from being recreated on every render. This can help to improve the performance of the component, especially when it's part of a larger application.
What is useMemo?
useMemo is a hook that gives you a memoized value. When a value is memoized, the value instance is cached and returned whenever the dependencies specified in the second argument of useMemo do not change. This can help you to avoid unnecessary memoized values that will be re-rendered whenever the function is called.
Here is an example...
In this example, we have a component MyComponent that has a count state and a memoized value result. The result value is memoized using useMemo because it's the result of an expensive calculation that depends on count.
In the calculateResult function, we're simply adding up all the numbers from 1 to count. This calculation can become expensive for large values of count, so it makes sense to memoize the result using useMemo.
By memoizing result, we can avoid unnecessary re-calculations of the value and improve the performance of the component. This can be particularly useful when the calculation is complex or resource-intensive, as in this example.
When to use useCallback
You should use useCallback when you need a function that is used as a prop for a child component. This can help to avoid unnecessary re-renders of a child component when the parent component re-renders.
When to use useMemo
You should use useMemo when you need to memoize a value that is expensive to calculate. This can help to avoid unnecessary re-calculations of the value when the component re-renders.
In conclusion, both useCallback and useMemo are important hooks that can help to optimize the performance of your React components and it's important to note that both hooks have different use cases and should be used appropriately based on your specific needs. Using them correctly can help to improve the performance of your React application and make it more efficient.