Flash cards
Review the key moves
What is the main idea behind React Suspense?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
___ { createRoot } from 'react-dom/client';Put the learning moves in the order that makes the concept easiest to apply.
React Suspense lets you display an alternative HTML while waiting for code or data to load.
The alternative HTML can be a component, text, or any valid content.
What is Suspense?
Suspense is a React feature that lets your components display an alternative HTML while waiting for code or data to load.
The most common use cases are
- Data fetching with suspense-enabled frameworks
- Loading components dynamically with React.lazy()
Using Suspense
If a component takes time to load, you can use a Suspense component, and it will display the fallback content while the component is loading.
Example
The Fruits component takes two seconds to load, so we wrap it in a Suspense component to display a loading message while it is loading.
import { createRoot } from 'react-dom/client';
import { Suspense } from 'react';
import Fruits from './Fruits';
function App() {
return ( <div> <Suspense fallback={<div>Loading...</div>}> <Fruits /> </Suspense> </div> );
}
createRoot(document.getElementById('root')).render( <App /> );Using Suspense with lazy Loading
Another common use of the Suspense component is when importing components with lazy loading:
In the example above we had to fake a delay of two seconds to see the loading message. A task like displaying three fruits from an array would be too fast to see the loading message at all.
But with lazy loading, we can import a component dynamically, and it will display a loading message while it is loading, even if the task is very fast.
Lets first create an example WITHOUT using lazy loading, where we do not fake a two seconds delay:
Example
This example is too fast to see the loading message:
import { createRoot } from 'react-dom/client';
import { Suspense } from 'react';
import Cars from './Cars';
function App() {
return ( <div> <Suspense fallback={<div>Loading...</div>}> <Cars /> </Suspense> </div> );
}
createRoot(document.getElementById('root')).render( <App /> );Now let us create an example WITH using lazy loading:
Example
Same example as above, but using lazy loading:
import { createRoot } from 'react-dom/client';
import { Suspense, lazy } from 'react';
const Cars = lazy(() => import('./Cars'));
function App() {
return ( <div> <Suspense fallback={<div>Loading...</div>}> <Cars /> </Suspense> </div> );
}
createRoot(document.getElementById('root')).render( <App /> );Example Explained
- lazy() lets you load a component dynamically
- Suspense shows a fallback while the component loads
Multiple Components
One Suspense component can wrap multiple lazy components:
Example
import { createRoot } from 'react-dom/client';
import { Suspense, lazy } from 'react';
const Header = lazy(() => import('./Header'));
const Content = lazy(() => import('./Content'));
const Sidebar = lazy(() => import('./Sidebar'));
function App() {
return ( <div> <Suspense fallback={<div>Loading...</div>}> <Header /> <div style={{ display: 'flex' }}> <Sidebar /> <Content /> </div> </Suspense> </div> );
}
createRoot(document.getElementById('root')).render( <App /> );