Profiling is an important technique to collect and show the time taken for a specific function to execute in the live environment. Profiling is normally use to find the performance bottleneck in a application. React provides two option to profile a react application

• Profiler Component

• Profiler DevTools

Profiler Component

React profiler component is just another react component used to record the profile information of a react component. Profiler component can be used anywhere in the react element tree. React accepts multiple profiler and multi-level nesting of the profiler. Let us check the signature and how to apply profiler in a react application in this chapter.

Signature of the Profiler component

Profiler component can nest any react component and requires two props,

• id

• Identifier for the profiler component

• onRender callback function

• Callback function called during each phase of the component rendering

The signature of the callback function is as follows −

function onRenderCallback(
   id,
   phase,
   actualDuration,
   baseDuration,
   startTime,
   commitTime,
   interactions
){
   // Do anything with the profiler information
}

An example callback function implementation to log the profiling data in the console is as follows −

const logProfilerData = (id, phase, actualTime, baseTime, startTime, commitTime) => {
   console.log(`${id}''s ${phase} phase:`);
   console.log(`Actual time: ${actualTime}`);
   console.log(`Base time: ${baseTime}`);
   console.log(`Start time: ${startTime}`);
   console.log(`Commit time: ${commitTime}`);
};

Applying Profiler

Let us create a new react application to learn how to apply Profiler component in this section.

First of all, create a new react application and start it using below command.

create-react-app myapp
cd myapp
npm start

Next, open App.css (src/App.css) and remove all CSS classes.

// remove all css classes

Next, create a simple hello component, Hello (src/Components/Hello.js) and render a simple message as shown below −

import React from "react";
class Hello extends React.Component {
   constructor(props) {
      super(props)
   }
   render() {
      return (
         <div>Hello, {this.props.name}</div>
      );
   }
}
export default Hello;

Here,

• Used name props to render the hello message with the given name

Next, open App component (src/App.js), and use profiler component as shown below −

import ''./App.css''
import React, { Profiler } from ''react'';
import Hello from ''./Components/Hello''
const logProfilerData = (id, phase, actualTime, baseTime, startTime, commitTime) => {
   console.log(`${id}''s ${phase} phase:`);
   console.log(`Actual time: ${actualTime}`);
   console.log(`Base time: ${baseTime}`);
   console.log(`Start time: ${startTime}`);
   console.log(`Commit time: ${commitTime}`);
};
function App() {
   return (
      <div className="container">
         <div style={{ padding: "10px" }}>
            <div>
               <Profiler id="helloWorld" onRender={logProfilerData}>
                  <Hello name="World" />
               </Profiler>
            </div>
         </div>
      </div>
   );
}
export default App;

Here,

• Imported Profiler component from the react package

• Used Hello component by wrapping it with Profiler component

• Created a callback function, logProfilerData and emitted all profiler data into the console

• Set the logProfilerData callback function in onRender props of Profiler component

Finally, open the application in the browser and check the final result. It will render the hello component as shown below −

Open the console and you can see the profiler information as shown below −

helloWorld''s mount phase:
App.js:7 Actual time: 4.900000000372529
App.js:8 Base time: 1.800000000745058
App.js:9 Start time: 515.7999999988824
App.js:10 Commit time: 525.9000000003725
...
App.js:6 helloWorld''s update phase:
App.js:7 Actual time: 1
App.js:8 Base time: 0.6999999992549419
App.js:9 Start time: 19836.900000000373
App.js:10 Commit time: 19838.400000000373

Profiler React DevTools

React DevTools plugin introduced a separate section for profiler. Developer can open the Profiler tab and get lot of useful insight about the application. Some of the feature available in profiler DevTools are as follows −

• Browsing commits

• Filtering commits

• Flame chart

• Ranked chart

• Component chart

Conclusion

React profiler component and profiler devtools are indispensible and powerful tools to profile and optimize a react application.