startWithDefined Function
Instantly emits a value from the provided getter if the value is defined.
If the getter returns an observable, the value will be emitted when the observable emits, but only
if no values have been emitted previously. Optionally, if nonNullish is set to true, null or
undefined values will not be emitted
@template T
The type of the values emitted by the observable
@template U
A subtype of T representing the specific value type emitted
@param getter: () => U | Observable<U>
A function that returns an initial value or an observable that emits the initial value
@param nonNullish?: boolean
If true, null or undefined values will not be emitted
@returns OperatorFunction<T, T>
API
function startWithDefined<T, U extends T>(
getter: () => U | Observable<U>,
nonNullish?: boolean,
): OperatorFunction<T, T>;Example
import {Subject} from 'rxjs';
import {Nullish} from '@bitfiber/utils';
import {startWithDefined} from '@bitfiber/rx';
const subject = new Subject<number | Nullish>();
subject.pipe(startWithDefined(() => 5))
.subscribe(v => console.log(v)); // expected result: 5
subject.pipe(startWithDefined(() => null))
.subscribe(v => console.log(v)); // expected result: null
subject.pipe(startWithDefined(() => null), true)
.subscribe(v => console.log(v)); // expected result: null value won`t be emitted
subject.pipe(startWithDefined(() => undefined))
.subscribe(v => console.log(v)); // expected result: undefined value won`t be emitted