lift.tsā¢1.11 kB
import { Observable } from '../Observable';
import { Subscriber } from '../Subscriber';
import { OperatorFunction } from '../types';
import { isFunction } from './isFunction';
/**
* Used to determine if an object is an Observable with a lift function.
*/
export function hasLift(source: any): source is { lift: InstanceType<typeof Observable>['lift'] } {
return isFunction(source?.lift);
}
/**
* Creates an `OperatorFunction`. Used to define operators throughout the library in a concise way.
* @param init The logic to connect the liftedSource to the subscriber at the moment of subscription.
*/
export function operate<T, R>(
init: (liftedSource: Observable<T>, subscriber: Subscriber<R>) => (() => void) | void
): OperatorFunction<T, R> {
return (source: Observable<T>) => {
if (hasLift(source)) {
return source.lift(function (this: Subscriber<R>, liftedSource: Observable<T>) {
try {
return init(liftedSource, this);
} catch (err) {
this.error(err);
}
});
}
throw new TypeError('Unable to lift unknown Observable type');
};
}