Ryan Pivovar rpivo

This API was removed in React 17

Interaction tracing with React

React recently introduced an experimental profiler API. After discussing this API with several teams at Facebook, one common piece of feedback was that the performance information would be more useful if it could be associated with the events that caused the application to render (e.g. button click, XHR response). Tracing these events (or "interactions") would enable more powerful tooling to be built around the timing information, capable of answering questions like "What caused this really slow commit?" or "How long does it typically take for this interaction to update the DOM?".

With version 16.4.3, React added experimental support for this tracing by way of a new NPM package, scheduler. However the public API for this package is not yet finalized and will likely change with upcoming minor releases, so it should be used with caution.

If you get an "Invalid name" error when you run npm init -y, rename the project folder to only contain lowercase ASCII letters or hyphens (e.g. my-project), and try again.

In production, it is recommended to minify any JavaScript code that is included with your application. Minification can help your website load several times faster, especially as the size of your JavaScript source code grows.

Here's one way to set it up:

Install Node.js
Run npm init -y in your project folder (don't skip this step!)
Run npm install terser

Now, to minify a file called like_button.js, run in the terminal:

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Usage

Profiler

React 16.4 will introduce a new Profiler component (initially exported as React.unstable_Profiler) for collecting render timing information in order to measure the "cost" of rendering for both sync and async modes.

Profiler timing metrics are significantly faster than those built around the User Timing API, and as such we plan to provide a production+profiling bundle in the future. (The initial release will only log timing information in DEV mode, although the component will still render its children- without timings- in production mode.)

How is it used?

Profiler can be declared anywhere within a React tree to measure the cost of rendering that portion of the tree. For example, a Navigation component and its descendants:

	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="UTF-8" />
	<title>Add React in One Minute</title>
	</head>
	<body>

	<h2>Add React in One Minute</h2>
	<p>This page demonstrates using React with no build tooling.</p>

	const rootHostContext = {};
	const childHostContext = {};

	const hostConfig = {
	now: Date.now,
	getRootHostContext: () => {
	return rootHostContext;
	},
	prepareForCommit: () => {},
	resetAfterCommit: () => {},

	import ReactReconciler from 'react-reconciler';

	const hostConfig = {};
	const ReactReconcilerInst = ReactReconciler(hostConfig);
	export default {
	render: (reactElement, domElement, callback) => {
	console.log(arguments);
	// Create a root Container if it doesnt exist
	if (!domElement._rootContainer) {
	domElement._rootContainer = ReactReconcilerInst.createContainer(domElement, false);

	/*
	A worklet for recording in sync with AudioContext.currentTime.

	More info about the API:
	https://developers.google.com/web/updates/2017/12/audio-worklet

	How to use:

	1. Serve this file from your server (e.g. put it in the "public" folder) as is.

	import babel from 'rollup-plugin-babel';
	import resolve from 'rollup-plugin-node-resolve';
	import commonjs from 'rollup-plugin-commonjs';
	import replace from 'rollup-plugin-replace';

	const env = process.env.NODE_ENV \|\| 'development';

	export default {
	input: [
	'src/index.js'