React code optimization guide: How to improve the running efficiency of front-end applications

React Code Optimization Guide: How to improve the operating efficiency of front-end applications

In front-end development, performance optimization has always been a key issue. Among JavaScript libraries and frameworks, React is currently the most widely used one, but if code optimization is not performed correctly, React applications may run slowly due to performance issues. This article will introduce some React code optimization methods and provide specific code examples.

1. Using PureComponent:

In React, there are two commonly used components: functional components and class components. Functional components are stateless and generally perform better than class components. Class components can use React's life cycle methods and states to manage the rendering of components. To improve performance, you can use PureComponent provided by React. PureComponent will compare whether the component's props and state have changed through shallow comparison to decide whether to re-render the component.

class MyComponent extends React.PureComponent {
  // ...
}

2. Avoid unnecessary re-rendering:

In React, the re-rendering of a component is triggered by changes in its props or state. However, not all props or state changes require the component to be re-rendered. Unnecessary re-rendering can be avoided by using the shouldComponentUpdate method or React.memo.

class MyComponent extends React.Component {
  shouldComponentUpdate(nextProps, nextState) {
    // 比较props或state是否有变化，返回布尔值决定是否重新渲染
  }
}

const MyComponent = React.memo(function MyComponent(props) {
  // 组件的渲染
});

3. Use batch updates:

In React, each modification of state will trigger the re-rendering of the component. In order to improve performance, you can use the setState callback function to implement batch updates.

this.setState((prevState) => ({ count: prevState.count + 1 }), () => {
  // 在回调函数中进行其他操作
});

4. Simplify the component structure:

The more complex the component structure is, the greater the rendering overhead will be. In order to improve performance, you can simplify the structure of components as much as possible and remove unnecessary nesting.

5. Using React Fragment:

In React, it is very common to wrap components with divs. However, extra divs may cause an increase in rendering levels, thus reducing performance. React Fragment can be used instead of div to reduce unnecessary rendering levels.

return (
  <React.Fragment>
    <Component1 />
    <Component2 />
  </React.Fragment>
);

6. Use lazy loading:

In React, you can use React.lazy and Suspense to implement lazy loading of components. Lazy loading can delay the loading of components, thereby reducing the time of initial rendering.

const MyComponent = React.lazy(() => import('./MyComponent'))

function App() {
  return (
    <div>
      <Suspense fallback={<div>Loading...</div>}>
        <MyComponent />
      </Suspense>
    </div>
  )
}

7. Use virtualization technology:

When the number of elements in the list is large, React's rendering performance may be affected. At this point, virtualization technologies such as react-virtualized or react-window can be used to optimize performance. Virtualization technology improves performance by rendering only visible elements.

The above are some common React code optimization methods, through which the operating efficiency of front-end applications can be improved. However, performance optimization is not static, and different projects may require different optimization strategies. Therefore, developers need to choose appropriate optimization methods to improve the performance of React applications based on specific project needs and performance issues.

Reference materials:

• React official documentation: https://reactjs.org/docs/optimizing-performance.html
• React.lazy and Suspense: https ://reactjs.org/docs/code-splitting.html#reactlazy
• react-virtualized： https://bvaughn.github.io/react-virtualized/
• react-window： https://react-window.now.sh/

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