REACT Profiler

React Profiler is a developer tool used to measure the performance of React components. It helps identify performance bottlenecks by showing how often components render and how long rendering takes.

What is React Profiler?

The React Profiler is a built-in tool in React that allows you to monitor:

• How long a component takes to render.
• How frequently components re-render.
• What triggered the rendering (e.g., props or state changes).

When to Use the React Profiler?

• Debugging performance issues.
• Optimizing components that re-render unnecessarily.
• Identifying components that take too long to render.

How to Enable React Profiler?

1. React Developer Tools:
   • Install the React Developer Tools browser extension (available for Chrome and Firefox).
   • Open your app in the browser, go to the “Profiler” tab in DevTools, and start profiling.
2. Profiler API (For Programmatic Profiling): React provides the <Profiler> component to measure rendering performance in your code.

Using the <Profiler> Component

Syntax

<Profiler id="ComponentName" onRender={callback}>
  <YourComponent />
</Profiler>

• id: A unique identifier for the Profiler.
• onRender: Callback function that provides performance data.

Example

import React, { Profiler, useState } from 'react';

const MyComponent = () => {
  return <div>Hello, Profiler!</div>;
};

const App = () => {
  const onRenderCallback = (
    id, // The "id" prop of the Profiler
    phase, // Either "mount" or "update"
    actualDuration, // Time taken to render the component
    baseDuration, // Estimated time to render without memoization
    startTime, // When React started rendering
    commitTime, // When React committed the update
    interactions // The interactions that triggered the render
  ) => {
    console.log(`Profiler [${id}] - Phase: ${phase}`);
    console.log(`Actual Duration: ${actualDuration}ms`);
  };

  return (
    <Profiler id="MyComponentProfiler" onRender={onRenderCallback}>
      <MyComponent />
    </Profiler>
  );
};

export default App;

What the onRender Callback Provides

• id: The name or ID of the Profiler.
• phase: "mount" (initial render) or "update" (re-render).
• actualDuration: The time taken to render the component subtree.
• baseDuration: The time taken to render the subtree without optimizations (e.g., memoization).
• startTime: Timestamp when React started rendering.
• commitTime: Timestamp when React committed the update.
• interactions: Information about the events that triggered the render.

Profiling in the Browser

Using React Developer Tools

1. Open your app in the browser.
2. Go to the “Profiler” tab in DevTools.
3. Click “Start Profiling” and interact with your app.
4. Stop profiling to view the rendering timeline and performance insights.

Best Practices with the Profiler

1. Combine with React.memo or useMemo: Optimize frequently re-rendering components.
2. Check Expensive Components: Use the Profiler to find components with high actualDuration.
3. Batch Updates: Minimize unnecessary renders by batching state updates using React’s useState or useReducer.
4. Monitor Critical Paths: Profile components involved in user interactions for the best performance gains.

Practical Example: Debugging Re-Renders

Problem:

A child component re-renders unnecessarily when its parent updates.

const Child = () => {
  console.log('Child rendered');
  return <p>Child component</p>;
};

const Parent = () => {
  const [count, setCount] = useState(0);

  return (
    <div>
      <button onClick={() => setCount(count + 1)}>Increment</button>
      <Child />
    </div>
  );
};

Solution:

Wrap the Child component with React.memo and use the Profiler to confirm:

const Child = React.memo(() => {
  console.log('Child rendered');
  return <p>Child component</p>;
});

const Parent = () => {
  const [count, setCount] = useState(0);

  return (
    <Profiler id="ParentProfiler" onRender={(id, phase, duration) => console.log(`${id} ${phase} - ${duration}ms`)}>
      <div>
        <button onClick={() => setCount(count + 1)}>Increment</button>
        <Child />
      </div>
    </Profiler>
  );
};

Tools to Pair with React Profiler

• React DevTools Profiler: Analyze in the browser.
• Web Vitals Library: Monitor user-centric performance metrics.
• Performance Monitoring Libraries: Tools like why-did-you-render to detect unnecessary re-renders.