Jonatan E. Salas JonatanSalas

A Redux Story

Developer: "Doo Doo Doo... Working on the new Redux rewrite. Gotta write some fetch actions..."

FETCH_USERS -> function fetchUsersAction() {...}
FETCH_PAGES -> function fetchPagesAction() {...}
FETCH_FRIENDS -> function fetchFriendsAction() {...}
FETCH_GROUPS -> function fetchGroupsAction() {...}
FETCH_EVENTS -> function fetchEventsAction() {...}

React recently introduced an experimental profiler API. This page gives instructions on how to use this API in a production release of your app.

Table of Contents

Profiling in production
- Create React App
- Webpack 4

Profiling in production

React DOM automatically supports profiling in development mode for v16.5+, but since profiling adds some small additional overhead it is opt-in for production mode. This gist explains how to opt-in.

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.

How we incorporate next and cloudfront (2018-04-21)

Feel free to contact me at [email protected] or tweet at me @statisticsftw

This is a rough outline of how we utilize next.js and S3/Cloudfront. Hope it helps!

It assumes some knowledge of AWS.

	import React, { useContext, useCallback } from 'react';

	export const FeatureFlagContext = React.createContext<string[]>([]);

	export const useFeatureFlag = () => {
	const features = useContext<string[]>(FeatureFlagContext);

	const hasFeature = useCallback(
	(feature: string) => {
	return features.includes(feature);

	// HOW TO RUN IT ON GOOGLE CHROME
	// 1. OPEN INSTAGRAM
	// 2. OPEN LIST OF FOLLOWERS
	// 3. OPEN DEVELOPER TOOLS
	// 4. COPY EVERYTHING HERE CTRL + A
	// 5. PASTE EVERYTHING IN DEVELOPER TOOLS CONSOLE
	// 6. CLICK ENTER
	// THERE YOU WILL SOON HAVE NO FRIENDS

	const FOLLOWING_BUTTON_TEXT = 'フォロー中' // CHANGE THIS TO YOUR LANGUAGE

	const App = createAppContainer(
	createStack({

	LoggedSwitch: createSwitch({

	// When user is authenticated
	LoggedIn: createStack({

	// The logged in root is generally a tab or drawer navigator
	LoggedInRoot: createTabsOrDrawer({

	import { useEffect, useRef } from 'react';

	function getItem(storage, key) {
	const value = storage.getItem(key);

	if (!value) return null;

	try {
	return JSON.parse(value);
	} catch (error) {

	let UserContext = React.createContext();

	class App extends React.Component {
	state = {
	user: null,
	setUser: user => {
	this.setState({ user });
	}
	};