Fragment (<>...</>)
The Fragment
component, which is often used via the <>...</>
syntax, lets you render multiple elements in place of one, without wrapping them in any other container element.
<>
<OneChild />
<AnotherChild />
</>
Usage
Returning multiple elements
Use Fragment
, or the equivalent <>...</>
syntax, to group multiple elements together. You can use it to put multiple elements in any place where a single element can go. For example, a component can only return one element, but by using a Fragment you can group multiple elements together and then return them as a group:
function Post() {
return (
<>
<PostTitle />
<PostBody />
</>
);
}
Fragments are useful because grouping elements with a Fragment has no effect on layout or styles, unlike if you wrapped the elements in some other container such as a DOM element. If you inspect this example with the browser tools, you’ll see that all <h1>
and <p>
DOM nodes appear as siblings without wrappers around them:
export default function Blog() { return ( <> <Post title="An update" body="It's been a while since I posted..." /> <Post title="My new blog" body="I am starting a new blog!" /> </> ) } function Post({ title, body }) { return ( <> <PostTitle title={title} /> <PostBody body={body} /> </> ); } function PostTitle({ title }) { return <h1>{title}</h1> } function PostBody({ body }) { return ( <article> <p>{body}</p> </article> ); }
Deep Dive
How to write a Fragment without the special syntax?
How to write a Fragment without the special syntax?
The example above is equivalent to importing Fragment
from React:
import { Fragment } from 'react';
function Post() {
return (
<Fragment>
<PostTitle />
<PostBody />
</Fragment>
);
}
Usually you won’t need this unless you need to pass a key
to your Fragment
.
Assigning multiple elements to a variable
Like any other element, you can assign Fragment elements to variables, pass them as props, and so on:
function CloseDialog() {
const buttons = (
<>
<OKButton />
<CancelButton />
</>
);
return (
<AlertDialog buttons={buttons}>
Are you sure you want to leave this page?
</AlertDialog>
);
}
Grouping elements with text
You can use Fragment
to group text together with components:
function DateRangePicker({ start, end }) {
return (
<>
From
<DatePicker date={start} />
to
<DatePicker date={end} />
</>
);
}
Rendering a list of Fragments
Here’s a situation where you need to write Fragment
explicitly instead of using the <></>
syntax. When you render multiple elements in a loop, you need to assign a key
to each element. If the elements within the loop are Fragments, you need to use the normal JSX element syntax in order to provide the key
attribute:
function Blog() {
return posts.map(post =>
<Fragment key={post.id}>
<PostTitle title={post.title} />
<PostBody body={post.body} />
</Fragment>
);
}
You can inspect the DOM to verify that there are no wrapper elements around the Fragment children:
import { Fragment } from 'react'; const posts = [ { id: 1, title: 'An update', body: "It's been a while since I posted..." }, { id: 2, title: 'My new blog', body: 'I am starting a new blog!' } ]; export default function Blog() { return posts.map(post => <Fragment key={post.id}> <PostTitle title={post.title} /> <PostBody body={post.body} /> </Fragment> ); } function PostTitle({ title }) { return <h1>{title}</h1> } function PostBody({ body }) { return ( <article> <p>{body}</p> </article> ); }
Reference
Fragment
Wrap elements in <Fragment>
to group them together in situations where you need a single element. Grouping elements in Fragment
has no effect on the resulting DOM; it is the same as if the elements were not grouped. The empty JSX tag <></>
is shorthand for <Fragment></Fragment>
in most cases.
Props
- optional
key
: Fragments declared with the explicit<Fragment>
syntax may have keys.
Caveats
If you want to pass
key
to a Fragment, you can’t use the<>...</>
syntax. You have to explicitly importFragment
from'react'
and render<Fragment key={yourKey}>...</Fragment>
.React does not reset state when you go from rendering
<><Child /></>
to[<Child />]
or back, or when you go from rendering<><Child /></>
to<Child />
and back. This only works a single level deep: for example, going from<><><Child /></></>
to<Child />
resets the state. See the precise semantics here.