Helpers

Reduce garbage collection burden.

pluckFirst

pluckFirst<TArr>(inputs$: Observable<TArr>): Observable<TArr[0]>

Map an Observable of Arraylike to an Observable of the first item.

Type parameters:

• TArr ArrayLike

Parameters:

Name	Type	Description
inputs$	Observable<TArr>	An Observable of arraylike.

Returns:

Observable<TArr[0]> Observable of the first item.

Examples:

// An Observable of string
const text$ = useObservable(pluckFirst, [props.text])

pluckCurrentTargetValue

pluckCurrentTargetValue<TEvent>(
  event$: Observable<TEvent>
): Observable<TEvent["currentTarget"]["value"]>

Maps an Observable of DOM events to an Observable of the currentTarget value.

Type parameters:

• TEvent Event with currentTarget.value.

Parameters:

Name	Type	Description
event$	Observable<TEvent>	An Observable of events.

Returns:

Observable<TEvent["currentTarget"]["value"]> An Observable of event currentTarget.value.

Examples:

const [onChange, textChange$] = useObservableCallback<
 string,
 React.FormEvent<HTMLInputElement>
>(pluckCurrentTargetValue)

pluckCurrentTargetChecked

pluckCurrentTargetChecked<TEvent>(
  event$: Observable<TEvent>
): Observable<TEvent["currentTarget"]["checked"]>

Maps an Observable of DOM events to an Observable of the currentTarget checked.

Type parameters:

• TEvent Event with currentTarget.checked.

Parameters:

Name	Type	Description
event$	Observable<TEvent>	An Observable of events.

Returns:

Observable<TEvent["currentTarget"]["checked"]> An Observable of event currentTarget.checked.

Examples:

const [onChange, checked$] = useObservableCallback<
 boolean,
 React.FormEvent<HTMLInputElement>
>(pluckCurrentTargetChecked)

identity

identity<T>(value: T): T

Returns the first argument it receives.

Type parameters:

• T Any value.

Parameters:

Name	Type	Description
value	T	Any value.

Returns:

T The first argument.

Type parameters:

• T any.

Parameters:

Name	Type	Description
init	(): T	A function that returns a value. Will be called only once.

Returns:

MutableRefObject<T> A Ref object with the returned value.

useForceUpdate

Force re-renders Component.

useForceUpdate(): () => void

Returns:

() => void A callback which re-renders component when called.