Kent C. Dodds kentcdodds

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.

Feel free to run via...

npx https://gist.github.com/elijahmanor/4cc8e3eac9fb5999c5d759388ff27c64

A series of posts on css-in-js

0. styles as objects

First, an exercise. Can we represent all of css with plain data? Let's try.

let redText = { color: 'red' };

ESM modules in node: npm edition

The proposal you’re about to read is not just a proposal. We have a working implementation of almost everything we discussed here. We encourage you to checkout and build our branch: our fork, with the relevant branch selected. Building and using the implementation will give you a better understanding of what using it as a developer is like.

Our implementation ended up differing from the proposal on some minor points. As our last action item before making a PR, we’re writing documentation on what we did. While I loathe pointing to tests in lieu of documentation, they will be helpful until we complete writing docs: the unit tests.

This repo also contains a bundled version of npm that has a new command, asset. You can read the documentation for and goals of that comma

	import React from "react";
	import useMutableReducer from "./useMutableReducer";

	const reducer = (draft, action, state) => {
	switch (action) {
	case "increment":
	draft.count++;
	break;
	case "decrement":
	draft.count--;

	/**
	* In our app, we have a few middleware that generate a string of HTML.
	* On occassion it's fine to just use dangerouslySetInnerHTML directly for
	* those, but that requires that you have a host node for the innerHTML.
	*
	* In certain scenarios (like tags in <head />), there's HTML that we need
	* to insert directly where it is. This component enables that because
	* we replace <raw-text> and </raw-text> with empty strings. Effectively
	* making whatever's between <raw-text> and </raw-text> inlined in place.
	*

	function logger(strings,...values) {
	var str = "";
	for (let i = 0; i < strings.length; i++) {
	if (i > 0) {
	if (values[i-1] && typeof values[i-1] == "object") {
	if (values[i-1] instanceof Error) {
	if (values[i-1].stack) {
	str += values[i-1].stack;
	continue;
	}

	[
	{
	"link": "https://blog.kentcdodds.com/migrating-to-jest-881f75366e7e",
	"title": "Migrating to Jest",
	"comment": "Kent C. Dodds is super excited about Jest as an alternative to AVA and Mocha, and explains how he was won over after not initially being a fan.",
	"newsletter": {
	"name": "JavaScript Weekly",
	"issue": 310,
	"link": "http://javascriptweekly.com/issues/310"
	}

	// Which of these things is the "Higher Order Component?"

	function withFoo(Component) { // <-- this is a function, not a component
	class Wrapper extends React.Component { // <-- this is a component
	static displayName = `withFoo(${Component.displayName \|\| Component.name})`
	static propTypes = {innerRef: PropTypes.func}
	static WrappedComponent = Component
	render() {
	const {innerRef, ...remainingProps} = this.props
	return <Component {...remainingProps} foo="FOO!" ref={innerRef} />

	<body>
	<div id="⚛️"></div>
	<script src="https://unpkg.com/[email protected]/umd/react.development.js"></script>
	<script src="https://unpkg.com/[email protected]/umd/react-dom.development.js"></script>
	<script src="https://unpkg.com/[email protected]/babel.js"></script>
	<script type="text/babel">
	ReactDOM.render(<div>Hello World!</div>, document.getElementById('⚛️'))
	</script>
	</body>