If you're as excited about React's new features as I am, you've probably been keeping an eye on the experimental builds. In this post, we're going to take an early look at an intriguing new feature that's not yet part of the official release: the useOptimistic
hook. This hook promises to simplify the way we handle optimistic updates in our React applications, making them feel snappier and more responsive. Let's explore how to use this experimental feature and consider the potential it has to enhance our user experience.
Experimental Disclaimer
Please note, at the time of writing, React
18.2.0
is the latest stable release, and theuseOptimistic
hook we're about to explore hasn't been officially released. The functionality is experimental, and there may be changes before its final release.
To experiment with the useOptimistic
hook, you'll need to install the experimental builds of react
and react-dom
. You can do this by running:
npm install react@experimental react-dom@experimental
And then import it like this:
import { experimental_useOptimistic as useOptimistic } from 'react';
If you're using TypeScript, remember to include "react/experimental"
in your tsconfig.json
file to ensure proper type recognition:
{
"compilerOptions": {
"types" ["react/experimental"]
}
}
Understanding Optimistic Updates
Optimistic updates aren't a new concept in web development, but they play a crucial role in enhancing user experience. This technique involves immediately updating the UI with expected changes, assuming that the corresponding server request will succeed. This creates the perception of a faster, more responsive application.
Here's how it typically works:
Imagine you have a list of todo items fetched from a server. When a user adds a new item, it requires a round trip to the server - which takes time. To make the UI feel faster, we can optimistically add the item to the list, making it appear as though the server has already confirmed the action. This is great in a perfect world, but we know network requests aren't always reliable. Handling potential errors and syncing state can become complex, which is where useOptimistic comes in, simplifying this process for React developers.
useOptimistic
in Action
This example could be used in both an NextJS SSR app and a traditional client-side React application.
Imagine we had a TodoList
component that contains a list of todo items and an input with a button to create a new todo item that gets added to the list.
Assume the TodoList
component has a todos
prop which is provided by data fetched from a server. We implement useOptimistic
to optimistically update the UI as follows:
import { experimental_useOptimistic as useOptimistic } from 'react'
import { v4 as uuid } from 'uuid'
import { createTodo } from './actions'
type TodoItem = {
id: string;
item: string;
}
export function TodoList({ todos }: { todos: TodoItem[] }) {
const [optimisticTodos, addOptimisticTodoItem] = useOptimistic<TodoItem[]>(
todos,
(state: TodoItem[], newTodoItem: string) => [
...state,
{ id: uuid(), item: newTodoItem },
]
)
return (
<div>
{optimisticTodos.map((todo) => (
<div key={todo.id}>{todo.item}</div>
))}
<form
action={async (formData: FormData) => {
const item = formData.get('item')
addOptimisticTodoItem(item)
await createTodo(item)
}}
>
<input type="text" name="item" />
<button type="submit">Add Item</button>
</form>
</div>
)
}
Breaking down the useOptimistic
hook
Let's look at the hook on its own with placeholder elements:
const [A, B] = useOptimistic<T>(C, D)
-
A
is the optimistic state, it will default to whatC
is. -
B
is the dispatching function to call that will run what we define inD
. -
C
is the source of truth, ifC
is ever changed i.e. we get a new value in from the server,A
will be set the that too since it will always treatC
as the final source of truth. -
D
is the mutation that will occur toA
whenB
is called. -
T
is an optional property for TypeScript users to define the type for the source of truth.
Additional Optimistic Properties
You can further leverage the useOptimistic
hook by including additional properties in the mutation.
For example, let's say we want a way to indicate that an update is optimistic to the user. We can do so by adding a pending: true
property to the optimistic update and render the todo item a gray
color until the update has properly occurred on the server.
We can do that by updating our initial example to this:
export function TodoList({ todos }: { todos: TodoItem[] }) {
const [optimisticTodos, addOptimisticTodoItem] = useOptimistic<TodoItem[]>(
todos,
(state: TodoItem[], newTodoItem: string) => [
...state,
{ item: newTodoItem, pending: true },
]
)
return (
<div>
{optimisticTodos.map((todo) => (
<div
key={todo.id}
style={{ color: todo.pending ? "gray" : "inherit" }}
>
{todo.item}
</div>
))}
<form
action={async (formData: FormData) => {
const item = formData.get('item')
addOptimisticTodoItem(item)
await createTodo(item)
}}
>
<input type="text" name="item" />
<button type="submit">Add Item</button>
</form>
</div>
)
}
Now when we submit a new todo item, optimistically our UI will update to the initial todo list plus one new todo item with the pending
property as true
. In our render method the pending
todo item will be styled to have a gray
color. Once the server update has occurred, the todos
prop - which is the source of truth - would have changed which will cause the optimisticTodos
value to update to the new source of truth. This new source of truth will include the optimistically updated value without the pending
property, so the new item will no longer have a gray
color.
Conclusion
While still experimental, the useOptimistic
hook offers an exciting glimpse into the future of state management in React applications. It aims to simplify the implementation of optimistic UI updates, contributing to faster, more responsive user experiences. This feature seems particularly promising when combined with NextJS's SSR capabilities, though it remains experimental at this stage.
As the React community anticipates the official release of this feature, I'm interested to hear your thoughts. Have you tried the useOptimistic
hook in your projects? What potential do you see for this feature in real-world applications? Share your experiences and insights in the comments below!
Top comments (11)
Wow. Thanks for sharing!
Iโm glad you found this interesting! Hopefully this prepares you for when it is properly ready! ๐ฅณ
Yesss. Thank you.
Looks awesome, thanks for the clear and consise explanation ๐
It's such a pleasure and thank you for the encouraging feedback!
Thank you @barrymichaeldoyle for this great explanation.
How do we handle errors? What to do when network request fails? Is there any mechanism to undo the optimistic update?
Sorry I've taken so long to get back to you.
The way the useOptimistic hook works is that the optimistic update resets when the the asynchronous form action is completed and the actual rendered value gets replaced by the new todos. It's not really shown in my example code in this post.
So in the case of an error - which will be handled in
createTodo
- the optimistic value will be cleared when the promise rejects because todos doesn't change. The way you decide to handle an error specifically is up to you e.g. you could render a toast, or show an error message under the todos list, up to you.Why useOptimistic is undefined in my app after I installed like so
npm install react@experimental react-dom@experimental
I tried import { useOptimistic } from 'react' as well but does not work.
It keeps erroring out saying
0__.useOptimistic) is not a function or its return value is not iterable
What if you mutate your data somewhere else? How would you use useOptimistic hook then? Perhaps, with state management libraries such as zustand?
You can wrap your action into a transition
`const [isPending, startTransition] = useTransition();
const onUpdate = () => {
startTransition(()=> {
optimisticUpdate();
})
}
`
In that scenario I'd recommend going with something like zustand yes.