react-error-boundary
Simple reusable React error boundary component
The problem
React v16 introduced the concept of “error boundaries”.
This solution
This component provides a simple and reusable wrapper that you can use to wrap around your components. Any rendering errors in your components hierarchy can then be gracefully handled.
Reading this blog post will help you understand what react-error-boundary does for you: Use react-error-boundary to handle errors in React – How to simplify your React apps by handling React errors effectively with react-error-boundary
Table of Contents
Installation
This module is distributed via npm which is bundled with node and should be installed as one of your project's dependencies
:
npm install --save react-error-boundary
Usage
The simplest way to use <ErrorBoundary>
is to wrap it around any component that may throw an error. This will handle errors thrown by that component and its descendants too.
import {ErrorBoundary} from 'react-error-boundary'
function ErrorFallback({error, resetErrorBoundary}) {
return (
<div role="alert">
<p>Something went wrong:</p>
<pre>{error.message}</pre>
<button onClick={resetErrorBoundary}>Try again</button>
</div>
)
}
const ui = (
<ErrorBoundary
FallbackComponent={ErrorFallback}
onReset={() => {
// reset the state of your app so the error doesn't happen again
}}
>
<ComponentThatMayError />
</ErrorBoundary>
)
You can react to errors (e.g. for logging) by providing an onError
callback:
import {ErrorBoundary} from 'react-error-boundary'
const myErrorHandler = (error: Error, info: {componentStack: string}) => {
// Do something with the error
// E.g. log to an error logging client here
}
const ui = (
<ErrorBoundary FallbackComponent={ErrorFallback} onError={myErrorHandler}>
<ComponentThatMayError />
</ErrorBoundary>,
)
You can also use it as a higher-order component:
import {withErrorBoundary} from 'react-error-boundary'
const ComponentWithErrorBoundary = withErrorBoundary(ComponentThatMayError, {
FallbackComponent: ErrorBoundaryFallbackComponent,
onError(error, info) {
// Do something with the error
// E.g. log to an error logging client here
},
})
const ui = <ComponentWithErrorBoundary />
Error Recovery
In the event of an error if you want to recover from that error and allow the user to "try again" or continue with their work, you'll need a way to reset the ErrorBoundary's internal state. You can do this various ways, but here's the most idiomatic approach:
function ErrorFallback({error, resetErrorBoundary}) {
return (
<div role="alert">
<p>Something went wrong:</p>
<pre>{error.message}</pre>
<button onClick={resetErrorBoundary}>Try again</button>
</div>
)
}
function Bomb() {
throw new Error('💥 CABOOM 💥')
}
function App() {
const [explode, setExplode] = React.useState(false)
return (
<div>
<button onClick={() => setExplode(e => !e)}>toggle explode</button>
<ErrorBoundary
FallbackComponent={ErrorFallback}
onReset={() => setExplode(false)}
resetKeys={[explode]}
>
{explode ? <Bomb /> : null}
</ErrorBoundary>
</div>
)
}
So, with this setup, you've got a button which when clicked will trigger an error. Clicking the button again will trigger a re-render which recovers from the error (we no longer render the <Bomb />
). We also pass the resetKeys
prop which is an array of elements for the ErrorBoundary
to check each render (if there's currently an error state). If any of those elements change between renders, then the ErrorBoundary
will reset the state which will re-render the children.
We have the onReset
prop so that if the user clicks the "Try again" button we have an opportunity to re-initialize our state into a good place before attempting to re-render the children.
This combination allows us both the opportunity to give the user something specific to do to recover from the error, and recover from the error by interacting with other areas of the app that might fix things for us. It's hard to describe here, but hopefully it makes sense when you apply it to your specific scenario.
API
ErrorBoundary
props
children
This is what you want rendered when everything's working fine. If there's an error that React can handle within the children of the ErrorBoundary
, the ErrorBoundary
will catch that and allow you to handle it gracefully.
FallbackComponent
This is a component you want rendered in the event of an error. As props it will be passed the error
and resetErrorBoundary
(which will reset the error boundary's state when called, useful for a "try again" button when used in combination with the onReset
prop).
This is required if no fallback
or fallbackRender
prop is provided.
fallbackRender
This is a render-prop based API that allows you to inline your error fallback UI into the component that's using the ErrorBoundary
. This is useful if you need access to something that's in the scope of the component you're using.
It will be called with an object that has error
and resetErrorBoundary
:
const ui = (
<ErrorBoundary
fallbackRender={({error, resetErrorBoundary}) => (
<div role="alert">
<div>Oh no</div>
<pre>{error.message}</pre>
<button
onClick={() => {
// this next line is why the fallbackRender is useful
resetComponentState()
// though you could accomplish this with a combination
// of the FallbackCallback and onReset props as well.
resetErrorBoundary()
}}
>
Try again
</button>
</div>
)}
>
<ComponentThatMayError />
</ErrorBoundary>
)
I know what you're thinking: I thought we ditched render props when hooks came around. Unfortunately, the current React Error Boundary API only supports class components at the moment, so render props are the best solution we have to this problem.
This is required if no FallbackComponent
or fallback
prop is provided.
fallback
In the spirit of consistency with the React.Suspense
component, we also support a simple fallback
prop which you can use for a generic fallback. This will not be passed any props so you can't show the user anything actually useful though, so it's not really recommended.
const ui = (
<ErrorBoundary fallback={<div>Oh no</div>}>
<ComponentThatMayError />
</ErrorBoundary>
)
onError
This will be called when there's been an error that the ErrorBoundary
has handled. It will be called with two arguments: error
, info
.
onReset
This will be called immediately before the ErrorBoundary
resets it's internal state (which will result in rendering the children
again). You should use this to ensure that re-rendering the children will not result in a repeat of the same error happening again.
onReset
will be called with whatever resetErrorBoundary
is called with.
Important: onReset
will not be called when reset happens from a change in resetKeys
. Use onResetKeysChange
for that.
resetKeys
Sometimes an error happens as a result of local state to the component that's rendering the error. If this is the case, then you can pass resetKeys
which is an array of values. If the ErrorBoundary
is in an error state, then it will check these values each render and if they change from one render to the next, then it will reset automatically (triggering a re-render of the children
).
See the recovery examples above.
onResetKeysChange
This is called when the resetKeys
are changed (triggering a reset of the ErrorBoundary
). It's called with the prevResetKeys
and the resetKeys
.
useErrorHandler(error?: Error)
React's error boundaries feature is limited in that the boundaries can only handle errors thrown during React's lifecycles. To quote the React docs on Error Boundaries:
Error boundaries do not catch errors for:
- Event handlers (learn more)
- Asynchronous code (e.g. setTimeout or requestAnimationFrame callbacks)
- Server side rendering
- Errors thrown in the error boundary itself (rather than its children)
This means you have to handle those errors yourself, but you probably would like to reuse the error boundaries you worked hard on creating for those kinds of errors as well. This is what useErrorHandler
is for.
There are two ways to use useErrorHandler
:
const handleError = useErrorHandler()
: callhandleError(theError)
useErrorHandler(error)
: useful if you are managing the error state yourself or get it from another hook.
Here's an example:
function Greeting() {
const [greeting, setGreeting] = React.useState(null)
const handleError = useErrorHandler()
function handleSubmit(event) {
event.preventDefault()
const name = event.target.elements.name.value
fetchGreeting(name).then(
newGreeting => setGreeting(newGreeting),
handleError,
)
}
return greeting ? (
<div>{greeting}</div>
) : (
<form onSubmit={handleSubmit}>
<label>Name</label>
<input id="name" />
<button type="submit">get a greeting</button>
</form>
)
}
Note, in case it's not clear what's happening here, you could also write
handleSubmit
like this:
function handleSubmit(event) {
event.preventDefault()
const name = event.target.elements.name.value
fetchGreeting(name).then(
newGreeting => setGreeting(newGreeting),
error => handleError(error),
)
}
Alternatively, let's say you're using a hook that gives you the error:
function Greeting() {
const [name, setName] = React.useState('')
const {greeting, error} = useGreeting(name)
useErrorHandler(error)
function handleSubmit(event) {
event.preventDefault()
const name = event.target.elements.name.value
setName(name)
}
return greeting ? (
<div>{greeting}</div>
) : (
<form onSubmit={handleSubmit}>
<label>Name</label>
<input id="name" />
<button type="submit">get a greeting</button>
</form>
)
}
In this case, if the error
is ever set to a truthy value, then it will be propagated to the nearest error boundary.
In either case, you could handle those errors like this:
const ui = (
<ErrorBoundary FallbackComponent={ErrorFallback}>
<Greeting />
</ErrorBoundary>
)
And now that'll handle your runtime errors as well as the async errors in the fetchGreeting
or useGreeting
code.
Issues
Looking to contribute? Look for the Good First Issue label.
🐛
Bugs
Please file an issue for bugs, missing documentation, or unexpected behavior.
💡
Feature Requests
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LICENSE
MIT