React Performance

Diagnose, profile, and fix performance problems in your React application using the Browser Profiler, React DevTools Profiler, and optimization techniques.

Element Optimization

Gain practical experience optimizing React component rendering.

Learn to hoist React elements to prevent unnecessary renders, pass elements as props, use React's Context API to trigger re-renders only on necessary state changes, and apply useMemo and React.memo.

Optimize Context

Here you'll learn three ways to optimize context: Memoize context values, create a provider component, and split context values into setter functions.

In addition to the techniques, this will teach you how to use the devtools to determine which ones you need to use.

Concurrent Rendering

Sometimes, you're rendering so many components or those components are doing such complex things that you can't afford to render them all quickly enough.

Find out how to use the useDeferredValue hook and memo to prioritize the rendering of some parts of your app over others.

Code Splitting

Code splitting acts on the principle that loading less code will speed up your app. There are three ways we'll approach it in this section:

Lazy loading, eager loading, and transitions.

In lazy loading you'll learn how to use React's lazy method for lazy loading components

Eager loading is like a layer on top of lazy loading. You'll learn how to deferr the loading of a component until some event occurs like a mouse over or on focus.

In transitions you'll learn to optimize the loading experience using the useTransition hook and the useSpinDelay hook from the spin-delay package.

Expensive Calculations

JavaScript is single-threaded which poses a problem when you need to deal with some kind of expensive calculation.

React has ways of dealing with this but if you are outside of React-land you'll be blocking the thread while the calculation is being performed. Luckily there are a couple options for dealing with this.

useMemo is useful if you're working with indempotent functions. And if you aren't, Web Workers let you perform the calculations on a separate thread but they add some complexity to your code.

Throughout this workshop you'll be learning to measure performance and weigh the trade-offs of all the techniques you learn!

Optimize Rendering

React is pretty smart about determining when it needs to re-render. But, sometimes there are cases we can get a bit of an edge over it ourselves.

If your components are re-rendering when a DOM update isn't actually needed, you'll want to reach for memo and memoize your components.

But, what if memo's built-in comparitor isn't doing the trick? It works off a simple Object.is. Which is great most of the time but if you're dealing with complex props you have the option of passing a custom comparitor function.

Windowing

And lastly you'll be exploring an advanced technique for when you're dealing with a truly massive amount of elements.

There's only so much optimizing you can do when you need to rendering thousands of elements. But, what if you only had to render a slice of them? That's where windowing comes in.

You'll be using the @tanstack/react-virtual library to virtualize only the visible DOM nodes (and a few nodes outside of view for the fast-scrollers) in a large scrollable element.