Class ErrorBoundary

context

static contextType = MyContext
// For TS pre-3.7:
context!: React.ContextType<typeof MyContext>
// For TS 3.7 and above:
declare context: React.ContextType<typeof MyContext>
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Readonlyprops

Static OptionalcontextType

type MyContext = number
const Ctx = React.createContext<MyContext>(0)

class Foo extends React.Component {
  static contextType = Ctx
  context!: React.ContextType<typeof Ctx>
  render () {
    return <>My context's value: {this.context}</>;
  }
}
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Static OptionalpropTypes

OptionalcomponentDidMount

• componentDidMount?(): void

  Called immediately after a component is mounted. Setting state here will trigger re-rendering.

  Returns void

OptionalcomponentWillMount

• componentWillMount?(): void

  Called immediately before mounting occurs, and before Component.render. Avoid introducing any side-effects or subscriptions in this method.

  Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.

  Returns void

  Deprecated

  16.3, use componentDidMount or the constructor instead; will stop working in React 17

  See

  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#initializing-state
  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#gradual-migration-path

OptionalcomponentWillReceiveProps

• componentWillReceiveProps?(nextProps: Readonly<P>, nextContext: any): void

  Called when the component may be receiving new props. React may call this even if props have not changed, so be sure to compare new and existing props if you only want to handle changes.

  Calling Component.setState generally does not trigger this method.

  Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.

  Parameters

  • nextProps: Readonly<P>
  • nextContext: any

  Returns void

  Deprecated

  16.3, use static StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps instead; will stop working in React 17

  See

  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#updating-state-based-on-props
  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#gradual-migration-path

OptionalcomponentWillUnmount

• componentWillUnmount?(): void

  Called immediately before a component is destroyed. Perform any necessary cleanup in this method, such as cancelled network requests, or cleaning up any DOM elements created in componentDidMount.

  Returns void

OptionalcomponentWillUpdate

• componentWillUpdate?(
      nextProps: Readonly<P>,
      nextState: Readonly<S>,
      nextContext: any,
  ): void

  Called immediately before rendering when new props or state is received. Not called for the initial render.

  Note: You cannot call Component.setState here.

  Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.

  Parameters

  • nextProps: Readonly<P>
  • nextState: Readonly<S>
  • nextContext: any

  Returns void

  Deprecated

  16.3, use getSnapshotBeforeUpdate instead; will stop working in React 17

  See

  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#reading-dom-properties-before-an-update
  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#gradual-migration-path

forceUpdate

• forceUpdate(callback?: () => void): void

  Parameters

  • Optionalcallback: () => void

  Returns void

OptionalgetSnapshotBeforeUpdate

• getSnapshotBeforeUpdate?(prevProps: Readonly<P>, prevState: Readonly<S>): any

  Runs before React applies the result of Component.render render to the document, and returns an object to be given to componentDidUpdate. Useful for saving things such as scroll position before Component.render render causes changes to it.

  Note: the presence of this method prevents any of the deprecated lifecycle events from running.

  Parameters

  • prevProps: Readonly<P>
  • prevState: Readonly<S>

  Returns any

setState

• setState<K extends "error">(
      state:
          | ErrorBoundaryState
          | (
              (
                  prevState: Readonly<S>,
                  props: Readonly<P>,
              ) => ErrorBoundaryState | Pick<ErrorBoundaryState, K> | null
          )
          | Pick<ErrorBoundaryState, K>
          | null,
      callback?: () => void,
  ): void

  Type Parameters

  • K extends "error"

  Parameters

  • state:
        | ErrorBoundaryState
        | (
            (
                prevState: Readonly<S>,
                props: Readonly<P>,
            ) => ErrorBoundaryState | Pick<ErrorBoundaryState, K> | null
        )
        | Pick<ErrorBoundaryState, K>
        | null
  • Optionalcallback: () => void

  Returns void

OptionalshouldComponentUpdate

• shouldComponentUpdate?(
      nextProps: Readonly<P>,
      nextState: Readonly<S>,
      nextContext: any,
  ): boolean

  Called to determine whether the change in props and state should trigger a re-render.

  Component always returns true. PureComponent implements a shallow comparison on props and state and returns true if any props or states have changed.

  If false is returned, Component.render, componentWillUpdate and componentDidUpdate will not be called.

  Parameters

  • nextProps: Readonly<P>
  • nextState: Readonly<S>
  • nextContext: any

  Returns boolean

OptionalUNSAFE_componentWillMount

• UNSAFE_componentWillMount?(): void

  Called immediately before mounting occurs, and before Component.render. Avoid introducing any side-effects or subscriptions in this method.

  This method will not stop working in React 17.

  Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.

  Returns void

  Deprecated

  16.3, use componentDidMount or the constructor instead

  See

  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#initializing-state
  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#gradual-migration-path

OptionalUNSAFE_componentWillReceiveProps

• UNSAFE_componentWillReceiveProps?(
      nextProps: Readonly<P>,
      nextContext: any,
  ): void

  Called when the component may be receiving new props. React may call this even if props have not changed, so be sure to compare new and existing props if you only want to handle changes.

  Calling Component.setState generally does not trigger this method.

  This method will not stop working in React 17.

  Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.

  Parameters

  • nextProps: Readonly<P>
  • nextContext: any

  Returns void

  Deprecated

  16.3, use static StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps instead

  See

  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#updating-state-based-on-props
  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#gradual-migration-path

OptionalUNSAFE_componentWillUpdate

• UNSAFE_componentWillUpdate?(
      nextProps: Readonly<P>,
      nextState: Readonly<S>,
      nextContext: any,
  ): void

  Called immediately before rendering when new props or state is received. Not called for the initial render.

  Note: You cannot call Component.setState here.

  This method will not stop working in React 17.

  Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.

  Parameters

  • nextProps: Readonly<P>
  • nextState: Readonly<S>
  • nextContext: any

  Returns void

  Deprecated

  16.3, use getSnapshotBeforeUpdate instead

  See

  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#reading-dom-properties-before-an-update
  • https://legacy.reactjs.org/blog/2018/03/27/update-on-async-rendering.html#gradual-migration-path