What are Pure Components in React?

In React, a pure component is a component that implements the shouldComponentUpdate() lifecycle method to optimize performance by skipping unnecessary updates.

Normally, when a component’s props or state changes, React will re-render the component to reflect the changes. However, this can be inefficient if the component does not actually need to be re-rendered, for example, if the changes do not affect the component’s output.

To optimize performance in these cases, you can use a pure component. A pure component is a component that implements the shouldComponentUpdate() method to shallowly compare the current props and state to the next props and state, and return false if they are equal. This tells React to skip the re-rendering of the component, which can improve performance in certain situations.

Here is an example of a pure component:

import React from 'react';

class MyComponent extends React.PureComponent {
  render() {
    // Render the component
  }
}

By extending React.PureComponent instead of React.Component, the MyComponent class will automatically implement the shouldComponentUpdate() method with a shallow prop and state comparison.

Pure components can be useful for optimizing performance in cases where the component does not need to re-render for every change in props or state, but they can also make it more difficult to reason about the behavior of the component if the comparison is not implemented correctly. As a result, it is important to use pure components with caution and only when necessary.