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, ReactPerf is a profiling tool that tells you exactly where you need to put these hooks.
Perf object documented here is exposed as
require('react-addons-perf') and can be used with React in development mode only. You should not include this bundle when building your app for production.
The dev build of React is slower than the prod build, due to all the extra logic for providing, for example, React's friendly console warnings (stripped away in the prod build). Therefore, the profiler only serves to indicate the relatively expensive parts of your app.
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() (described below) to get the measurements.
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,
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
printOperations() which is described in the previous paragraph. Currently
printDOM() still exists as an alias but it prints a deprecation warning and will eventually be removed.
The above print methods use
Perf.getLastMeasurements() to pretty-print the result.
Get the opaque data structure describing measurements from the last start-stop session. You can save it and pass it to the methods above 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.