import Perf from 'react-addons-perf' // ES6 var Perf = require('react-addons-perf') // ES5 with npm var Perf = React.addons.Perf; // ES5 with react-with-addons.js
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() hook 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 hooks.
See these articles by the Benchling Engineering Team for a in-depth introduction to performance tooling:
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.
Perf object can be used with React in development mode only. You should not include this bundle when building your app for production.
The following methods use the measurements returned by
Perf.getLastMeasurements() to pretty-print the result.
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.
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.
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.
Prints the overall time taken. If no argument's passed, defaults to all the measurements from the last recording. This prints a nicely formatted table in the console, like so:
"Exclusive" times don't include the times taken to mount the components: processing props, calling
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.
Prints the underlying DOM manipulations, e.g. "set innerHTML" and "remove".
This method has been renamed to
printDOM() still exists as an alias but it prints a deprecation warning and will eventually be removed.