Performance Tools

Note:

As of React 16, react-addons-perf is not supported. Please use your browser’s profiling tools to get insight into which components re-render.

Importing

import Perf from 'react-addons-perf'; // ES6
var Perf = require('react-addons-perf'); // ES5 with npm

Overview

React is usually quite fast out of the box. However, in situations where you need to squeeze every ounce of performance out of your app, it provides a shouldComponentUpdate() method where you can add optimization hints to React’s diff algorithm.

In addition to giving you an overview of your app’s overall performance, Perf is a profiling tool that tells you exactly where you need to put these methods.

See these articles for an introduction to React performance tooling:

• “How to Benchmark React Components”
• “Performance Engineering with React”
• “A Deep Dive into React Perf Debugging”

Development vs. Production Builds

If you’re benchmarking or seeing performance problems in your React apps, make sure you’re testing with the minified production build. The development build includes extra warnings that are helpful when building your apps, but it is slower due to the extra bookkeeping it does.

However, the perf tools described on this page only work when using the development build of React. Therefore, the profiler only serves to indicate the relatively expensive parts of your app.

Using Perf

The Perf object can be used with React in development mode only. You should not include this bundle when building your app for production.

Getting Measurements

• start()
• stop()
• getLastMeasurements()

Printing Results

The following methods use the measurements returned by Perf.getLastMeasurements() to pretty-print the result.

• printInclusive()
• printExclusive()
• printWasted()
• printOperations()
• printDOM()

Reference

start()

stop()

Perf.start()
// ...
Perf.stop()

Start/stop the measurement. The React operations in-between are recorded for analyses below. Operations that took an insignificant amount of time are ignored.

After stopping, you will need Perf.getLastMeasurements() to get the measurements.

getLastMeasurements()

Perf.getLastMeasurements()

Get the opaque data structure describing measurements from the last start-stop session. You can save it and pass it to the other print methods in Perf to analyze past measurements.

Note

Don’t rely on the exact format of the return value because it may change in minor releases. We will update the documentation if the return value format becomes a supported part of the public API.

printInclusive()

Perf.printInclusive(measurements)

Prints the overall time taken. When no arguments are passed, printInclusive defaults to all the measurements from the last recording. This prints a nicely formatted table in the console, like so:

printExclusive()

Perf.printExclusive(measurements)

“Exclusive” times don’t include the times taken to mount the components: processing props, calling componentWillMount and componentDidMount, etc.

printWasted()

Perf.printWasted(measurements)

The most useful part of the profiler.

“Wasted” time is spent on components that didn’t actually render anything, e.g. the render stayed the same, so the DOM wasn’t touched.

printOperations()

Perf.printOperations(measurements)

Prints the underlying DOM manipulations, e.g. “set innerHTML” and “remove”.

printDOM()

Perf.printDOM(measurements)

This method has been renamed to printOperations(). Currently printDOM() still exists as an alias but it prints a deprecation warning and will eventually be removed.