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>
Static Optional contextIf set, this.context will be set at runtime to the current value of the given Context.
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}</>;
}
}
https://react.dev/reference/react/Component#static-contexttype
Optional UNSAFE_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.
Optional UNSAFE_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.
Optional UNSAFE_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.
16.3, use getSnapshotBeforeUpdate instead
Optional componentCatches exceptions generated in descendant components. Unhandled exceptions will cause the entire component tree to unmount.
Optional componentCalled immediately after updating occurs. Not called for the initial render.
The snapshot is only present if getSnapshotBeforeUpdate is present and returns non-null.
Optional snapshot: anyOptional componentCalled 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.
Optional componentCalled 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.
Optional componentCalled 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.
16.3, use getSnapshotBeforeUpdate instead; will stop working in React 17
Optional getRuns 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.
Optional shouldCalled 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.
If using the new style context, re-declare this in your class to be the
React.ContextTypeof yourstatic contextType. Should be used with type annotation or static contextType.