38 lines
1.6 KiB
TypeScript
38 lines
1.6 KiB
TypeScript
import { Observable } from '../Observable';
|
|
import { OperatorFunction } from '../interfaces';
|
|
/**
|
|
* Emits only the index of the first value emitted by the source Observable that
|
|
* meets some condition.
|
|
*
|
|
* <span class="informal">It's like {@link find}, but emits the index of the
|
|
* found value, not the value itself.</span>
|
|
*
|
|
* <img src="./img/findIndex.png" width="100%">
|
|
*
|
|
* `findIndex` searches for the first item in the source Observable that matches
|
|
* the specified condition embodied by the `predicate`, and returns the
|
|
* (zero-based) index of the first occurrence in the source. Unlike
|
|
* {@link first}, the `predicate` is required in `findIndex`, and does not emit
|
|
* an error if a valid value is not found.
|
|
*
|
|
* @example <caption>Emit the index of first click that happens on a DIV element</caption>
|
|
* var clicks = Rx.Observable.fromEvent(document, 'click');
|
|
* var result = clicks.findIndex(ev => ev.target.tagName === 'DIV');
|
|
* result.subscribe(x => console.log(x));
|
|
*
|
|
* @see {@link filter}
|
|
* @see {@link find}
|
|
* @see {@link first}
|
|
* @see {@link take}
|
|
*
|
|
* @param {function(value: T, index: number, source: Observable<T>): boolean} predicate
|
|
* A function called with each item to test for condition matching.
|
|
* @param {any} [thisArg] An optional argument to determine the value of `this`
|
|
* in the `predicate` function.
|
|
* @return {Observable} An Observable of the index of the first item that
|
|
* matches the condition.
|
|
* @method find
|
|
* @owner Observable
|
|
*/
|
|
export declare function findIndex<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): OperatorFunction<T, number>;
|