Hi Brendan, according to Ricky from React (Rick Hanlonii)
In React 18 we’re introducing a new API that helps keep your app responsive even during large screen updates. This new API lets you substantially improve user interactions by marking specific updates as “transitions”. React will let you provide visual feedback during a state transition and keep the browser responsive while a transition is happening.
What problem does this solve?
Building apps that feel fluid and responsive is not always easy. Sometimes, small actions like clicking a button or typing into an input can cause a lot to happen on screen. This can cause the page to freeze or hang while all of the work is being done.
For example, consider typing in an input field that filters a list of data. You need to store the value of the field in state so that you can filter the data and control the value of that input field. Your code may look something like this:
// Update the input value and search results
setSearchQuery(input);
Here, whenever the user types a character, we update the input value and use the new value to search the list and show the results. For large screen updates, this can cause lag on the page while everything renders, making typing or other interactions feel slow and unresponsive. Even if the list is not too long, the list items themselves may be complex and different on every keystroke, and there may be no clear way to optimize their rendering.
Conceptually, the issue is that there are two different updates that need to happen. The first update is an urgent update, to change the value of the input field and, potentially, some UI around it. The second, is a less urgent update to show the results of the search.
// Urgent: Show what was typed
setInputValue(input);
// Not urgent: Show the results
setSearchQuery(input);
Users expect the first update to be immediate because the native browser handling for these interactions is fast. But the second update may be a bit delayed. Users don't expect it to complete immediately, which is good because there may be a lot of work to do. (In fact, developers often artificially delay such updates with techniques like debouncing.)
Until React 18, all updates were rendered urgently. This means that the two state states above would still be rendered at the same time, and would still block the user from seeing feedback from their interaction until everything rendered. What we’re missing is a way to tell React which updates are urgent, and which are not.
How does startTransition help?
The new startTransition API solves this issue by giving you the ability to mark updates as “transitions”:
import { startTransition } from 'react';
// Urgent: Show what was typed
setInputValue(input);
// Mark any state updates inside as transitions
startTransition(() => {
// Transition: Show the results
setSearchQuery(input);
});
Updates wrapped in startTransition are handled as non-urgent and will be interrupted if more urgent updates like clicks or key presses come in. If a transition gets interrupted by the user (for example, by typing multiple characters in a row), React will throw out the stale rendering work that wasn’t finished and render only the latest update.
Transitions lets you keep most interactions snappy even if they lead to significant UI changes. They also let you avoid wasting time rendering content that's no longer relevant.
Hi Brendan, according to Ricky from React (Rick Hanlonii)
In React 18 we’re introducing a new API that helps keep your app responsive even during large screen updates. This new API lets you substantially improve user interactions by marking specific updates as “transitions”. React will let you provide visual feedback during a state transition and keep the browser responsive while a transition is happening.
What problem does this solve?
Building apps that feel fluid and responsive is not always easy. Sometimes, small actions like clicking a button or typing into an input can cause a lot to happen on screen. This can cause the page to freeze or hang while all of the work is being done.
For example, consider typing in an input field that filters a list of data. You need to store the value of the field in state so that you can filter the data and control the value of that input field. Your code may look something like this:
// Update the input value and search results
setSearchQuery(input);
Here, whenever the user types a character, we update the input value and use the new value to search the list and show the results. For large screen updates, this can cause lag on the page while everything renders, making typing or other interactions feel slow and unresponsive. Even if the list is not too long, the list items themselves may be complex and different on every keystroke, and there may be no clear way to optimize their rendering.
Conceptually, the issue is that there are two different updates that need to happen. The first update is an urgent update, to change the value of the input field and, potentially, some UI around it. The second, is a less urgent update to show the results of the search.
// Urgent: Show what was typed
setInputValue(input);
// Not urgent: Show the results
setSearchQuery(input);
Users expect the first update to be immediate because the native browser handling for these interactions is fast. But the second update may be a bit delayed. Users don't expect it to complete immediately, which is good because there may be a lot of work to do. (In fact, developers often artificially delay such updates with techniques like debouncing.)
Until React 18, all updates were rendered urgently. This means that the two state states above would still be rendered at the same time, and would still block the user from seeing feedback from their interaction until everything rendered. What we’re missing is a way to tell React which updates are urgent, and which are not.
How does startTransition help?
The new startTransition API solves this issue by giving you the ability to mark updates as “transitions”:
import { startTransition } from 'react';
// Urgent: Show what was typed
setInputValue(input);
// Mark any state updates inside as transitions
startTransition(() => {
// Transition: Show the results
setSearchQuery(input);
});
Updates wrapped in startTransition are handled as non-urgent and will be interrupted if more urgent updates like clicks or key presses come in. If a transition gets interrupted by the user (for example, by typing multiple characters in a row), React will throw out the stale rendering work that wasn’t finished and render only the latest update.
Transitions lets you keep most interactions snappy even if they lead to significant UI changes. They also let you avoid wasting time rendering content that's no longer relevant.
Thanks @michelledev3 , very well explained