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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Readonly props

refs

state

Static Optional contextType

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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Optional UNSAFE_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 getDerivedStateFromProps prevents this from being invoked.

  Deprecated

  16.3, use componentDidMount or the constructor instead

  See

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

  Returns void

Optional UNSAFE_componentWillReceiveProps

• UNSAFE_componentWillReceiveProps(nextProps, nextContext): 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 getDerivedStateFromProps prevents this from being invoked.

  Deprecated

  16.3, use static getDerivedStateFromProps instead

  See

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

  Parameters

  • nextProps: Readonly<P>

  • nextContext: any

  Returns void

Optional UNSAFE_componentWillUpdate

• UNSAFE_componentWillUpdate(nextProps, nextState, nextContext): 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 getDerivedStateFromProps prevents this from being invoked.

  Deprecated

  16.3, use getSnapshotBeforeUpdate instead

  See

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

  Parameters

  • nextProps: Readonly<P>

  • nextState: Readonly<{}>

  • nextContext: any

  Returns void

Optional componentDidCatch

• componentDidCatch(error, errorInfo): void

• Catches exceptions generated in descendant components. Unhandled exceptions will cause the entire component tree to unmount.

  Parameters

  • error: Error

  • errorInfo: ErrorInfo

  Returns void

Optional componentDidUpdate

• componentDidUpdate(prevProps, prevState, snapshot?): void

• Called immediately after updating occurs. Not called for the initial render.

  The snapshot is only present if getSnapshotBeforeUpdate is present and returns non-null.

  Parameters

  • prevProps: Readonly<P>

  • prevState: Readonly<{}>

  • Optional snapshot: any

  Returns void

Optional componentWillMount

• 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 getDerivedStateFromProps prevents this from being invoked.

  Deprecated

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

  See

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

  Returns void

Optional componentWillReceiveProps

• componentWillReceiveProps(nextProps, nextContext): 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 getDerivedStateFromProps prevents this from being invoked.

  Deprecated

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

  See

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

  Parameters

  • nextProps: Readonly<P>

  • nextContext: any

  Returns void

Optional componentWillUnmount

• 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

Optional componentWillUpdate

• componentWillUpdate(nextProps, nextState, nextContext): 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 getDerivedStateFromProps prevents this from being invoked.

  Deprecated

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

  See

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

  Parameters

  • nextProps: Readonly<P>

  • nextState: Readonly<{}>

  • nextContext: any

  Returns void

forceUpdate

• forceUpdate(callback?): void

• Parameters

  • Optional callback: (() => void)

    • • (): void

      • Returns void

  Returns void

Optional getSnapshotBeforeUpdate

• getSnapshotBeforeUpdate(prevProps, prevState): any

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

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

  Parameters

  • prevProps: Readonly<P>

  • prevState: Readonly<{}>

  Returns any

setState

• setState<K>(state, callback?): void

• Type parameters

  Type Parameters

  • K extends never

  Parameters

  • state: {} | ((prevState, props) => {} | Pick<{}, K>) | Pick<{}, K>

  • Optional callback: (() => void)

    • • (): void

      • Returns void

  Returns void