Mastering React Performance: A Simple Guide to useMemo

I’m Suki, front-end developer. In this blog, I would like to share with you about the benefit of using useMemo in React and uncover how useMemo can be a game-changer in fine-tuning the performance of your React components.

What is useMemo?

useMemo is a React hook that memorizes the result of a function and returns the cached result when the dependencies (specifies as an array) remain unchanged. This can prevent unnecessary recalculations and re-renders, optimizing performance.

When to Use useMemo?

• Expensive Computations: When a component involves computations that are resource-intensive or time-consuming.
• Preventing Unnecessary Re-renders: To avoid re-rendering a component when its output remains the same based on certain conditions.

Practical Examples: When useMemo Shines.

1. Optimizing expensive calculations:

Considering the scenario where a component performs complex mathematical calculations. Without memoization, these calculations would be executed on every render, even if the inputs remain constant.

Let’s break down the example to explain how useMemo works and how it can optimize the performance of a React component.

• Component Structure: we have a functional component named ExpensiveCalculationComponent that takes a prop called value.
• Calculating Expensive Values: within the component, there’s a function performExpensiveCalculation that presumably performs complex or resource-intensive calculations based on the value prop.
• Using useMemo: the crucial part is the use of the useMemo hook. It takes two arguments. The first argument is a function that contains the expensive calculation. And the second argument is an array of dependencies that the calculation relies on ([value]).

How useMemo works in the above example ?

1. On Initial Render:

• When the component initially renders, useMemo executes the provided function (performExpensiveCalculation(value)).
• It then caches the result of that function

2. On Subsequent Renders:

• On subsequent renders, useMemo checks if any of dependencies specified in the dependency array ([value]) have changed.
• If the dependencies have not changed, it returns the cached result without re-executing the function.
• If the dependencies have changed, it re-executes the function, updates the cache, and returns the new result.

Optimizing performance.

• Scenario Without useMemo: without using useMemo , the expensive calculation would occur on every render, regardless of whether the value has changed or not. This could lead to unnecessary computations and performance overhead.
• Scenario With useMemo: with useMemo , the expensive calculation is only performed when the value prop changes. If the value remains the same between renders, the cached result is returned, preventing redundant calculations and improving performance.

2. Memoizing components

useMemo can also be applied to memoize entire components, preventing them from re-rendering unless necessary.

Performance Considerations And Best Practices

1. Avoid overusing useMemo

While useMemo is powerful, excessive usage can lead to unnecessary complexity. Use it judiciously for scenarios where performance gains are significant.

2. Dependency Array Precision

Be precise and specifying the dependency array. Including unnecessary dependencies might lead to unexpected behaviour. Use tools like ESLint plugins to catch missing dependencies.

3. Benchmarking and Profiling

Always benchmark and profile your application to validate the performance improvements gained from using useMemo. Tools like React DevTools can help analyze rendering times.

In conclusion, useMemo emerges as a valuable ally. By intelligently leveraging this hook, you can transform data-heavy components into streamlined powerhouses. Remember, the key lies in understanding when and how to apply useMemo to achieve the perfect balance between computation efficiency and a responsive user interface.

Thanks for reading ❤️😊.