Component vs. Purecomponent React

React, a well-liked JavaScript toolkit for building user interface, gives developers access to an extensive set of tools and capabilities. Among the many elements React offers, Component and PureComponent stand out as two noticeable ones. Although they might initially seem to be the same, there are major differences between them that have an impact on how your React software functions and behaves. In order for you to make an informed decision between Component and PureComponent, we will study these differences in this post.

What are Components and PureComponents?

Before diving into the differences, let's briefly understand what Component and PureComponent are in React.

Component:

A Component is the bottom class from which every custom component in React is derived. By using setState(), you can create your personal components that may handle lifecycle functions, sustain state, and change the user interface. A component may only compare props and state casually to decide whether to re-render or not.

PureComponent:

PureComponent, on the other hand, is a better Component. It immediately implements the shouldComponentUpdate function after giving the props and state a brief inspection. It avoids unneeded re-rendering if little changes, which could enhance performance. When using PureComponent, you get the same features as a Component but with an additional layer of speed marketing.

The Difference in Re-rendering Mechanism:

The primary distinction between Component and PureComponent lies in their re-rendering mechanism.

Component:

A component that extends the Component class will re-render whenever setState() is used or whenever it receives new props. Re-rendering can be very resource-intensive, especially when the component is a part of an extensive application that frequently changes its state.

PureComponent:

PureComponent performs a shallow comparison of props and state before triggering a re-render. It only re-renders if there are actual changes in the prop or state values. This behavior significantly reduces the number of re-renders, making it more efficient than a regular Component.

When to Use Component or PureComponent:

Choosing between Component and PureComponent depends on the specific requirements and use cases of your React application.

Use Component When:

You need to frequently update the UI based on state changes, even when the new state values are identical to the previous ones.

The component has a relatively simple structure with minimal data or props.

You want to have full control over the re-rendering process, and the performance overhead is not a concern.

Use PureComponent When:

Your component receives a large number of props or complex data structures that might trigger frequent re-renders.

You want to optimize your application's performance and reduce unnecessary re-renders.

The component is not reliant on external state changes and can be efficiently controlled by its own internal state.

Caveats and Warnings:

While using PureComponent can enhance the performance of your application, it's essential to keep in mind a few caveats:

• Shallow comparison may not be sufficient for deeply nested data structures. In such cases, you might need to implement custom shouldComponentUpdate logic or use more advanced solutions like memoization or immutable data structures.
• Avoid using PureComponent for components that rely heavily on asynchronous data fetching or side effects. The shallow comparison may not capture changes in these cases, leading to incorrect behavior.

Shallow Comparison in PureComponent:

As mentioned earlier, PureComponent performs a shallow comparison of props and state to determine whether a re-render is necessary. This means that it compares the references of the props and state objects rather than their contents. If any of the references change, PureComponent assumes that the data might have changed and triggers a re-render. However, it does not perform a deep comparison of the objects' content.

This can lead to some potential issues if the props or states are complex data structures with nested objects or arrays. Since PureComponent only checks the top-level references, changes within the nested objects or arrays might not be detected, and the component won't re-render as expected. In such cases, you should consider implementing a custom shouldComponentUpdate logic or using specialized libraries for deep comparison, like memoize-one or immutable.js.

Performance Considerations:

Using PureComponent can be highly beneficial for components that receive numerous props or complex data structures. By avoiding unnecessary re-renders, you can improve the overall performance of your React application, especially in scenarios where the UI updates frequently due to data changes.

However, it's important to strike a balance between performance and complexity. While PureComponent can be more efficient, using it indiscriminately for all components may not always yield significant benefits. Smaller components with simple structures might not experience noticeable performance improvements, and using PureComponent for them could lead to unnecessary overhead. Additionally, constantly updating the component's props or state might reduce the benefits of using PureComponent.

Avoiding PureComponent Pitfalls:

Although PureComponent can be an excellent performance optimization tool, there are situations where its usage might lead to unexpected results. Here are some common pitfalls to be aware of:

1. Mutating State or Props: If you directly mutate the state or props, React's shallow comparison won't detect the changes, and the PureComponent won't re-render. Always ensure that you update the state or props immutably using methods like Object.assign or the spread operator.
2. Asynchronous Updates: Components relying on asynchronous data fetching, timers, or side effects might not work well with PureComponent. Since PureComponent only performs shallow comparisons during its shouldComponentUpdate check, it won't catch changes happening asynchronously.
3. Inline Functions as Props: Be cautious when passing inline functions as props to PureComponent children. Each time the parent component renders, a new instance of the inline function is created, resulting in different function references for the same logic, which can cause unnecessary re-renders. Use React.memo or extract the function to a separate component to mitigate this issue.

Memoization and Advanced Optimizations:

For complex components where PureComponent may not be sufficient, you can explore other optimization techniques, such as memoization and custom shouldComponentUpdate logic.

1. Memoization: Use libraries like memoize-one or reselect to cache the results of expensive computations and avoid recomputing them unless the inputs change. Memoization ensures that your components re-render only when necessary and can significantly improve performance for computationally intensive components.
2. Custom shouldComponentUpdate: For components that require deep comparisons or have specific re-rendering requirements, you can manually implement the shouldComponentUpdate method. This allows you to have full control over the re-rendering logic and can be more efficient in some scenarios.

Choosing the Right Approach:

Ultimately, the choice between using Component or PureComponent in your React application depends on understanding the characteristics and demands of your components.

Use Component when you need to have fine-grained control over the re-rendering process, and performance optimizations are not a top priority.

Use PureComponent when your component receives many props or has a complex structure that can lead to frequent re-renders. This will help reduce unnecessary rendering and enhance your application's performance.

For highly specialized use cases, consider combining PureComponent with memoization or custom shouldComponentUpdate logic to achieve advanced optimization and control over re-rendering.

Use Cases for Component and PureComponent:

Component:

• Components with infrequent updates: If a component rarely updates its state or receives new props, using a regular Component might be sufficient. The shallow comparison overhead won't impact performance significantly if re-renders are minimal.
• Controlled components: In controlled components, where the component's state is directly tied to its props, using a Component is often more straightforward and easier to reason about.

PureComponent:

• Lists and data-driven components: Components rendering lists of items or receiving large datasets as props can benefit greatly from using PureComponent. It reduces re-renders when the data remains unchanged, leading to smoother user experiences.
• Presentation components: For components responsible for rendering UI without much internal state management or complex logic, using PureComponent can be a straightforward optimization.

Best Practices and Recommendations:

1. Avoid premature optimization: Always prioritize writing clean and maintainable code first. Only optimize using PureComponent or other techniques when performance issues arise and can be objectively measured.
2. Use React DevTools: React DevTools can help you profile your application and identify components that trigger frequent re-renders. This information can guide you in deciding which components would benefit from using PureComponent.
3. Memoization when needed: In addition to PureComponent, consider using memoization libraries like memoize-one or reselect for fine-grained control over re-rendering and performance improvements.
4. Measure performance: Benchmark and profile your application to ensure that using PureComponent or other optimizations indeed provide noticeable performance gains. Sometimes, the improvements may be marginal and not worth the added complexity.
5. Know your data: Be mindful of the data structures passed as props and state to your components. Understand their shapes and nested structures to determine if shallow comparison is sufficient or if custom shouldComponentUpdate logic is necessary.
6. Test thoroughly: As with any optimization, thorough testing is essential. Test the components with different scenarios and edge cases to ensure that the re-rendering behavior is as expected and no bugs are introduced.