import { Observable } from '../Observable'; import { Falsy, OperatorFunction } from '../types'; import { operate } from '../util/lift'; import { createFind } from './find'; export function findIndex(predicate: BooleanConstructor): OperatorFunction; /** @deprecated Use a closure instead of a `thisArg`. Signatures accepting a `thisArg` will be removed in v8. */ export function findIndex(predicate: BooleanConstructor, thisArg: any): OperatorFunction; /** @deprecated Use a closure instead of a `thisArg`. Signatures accepting a `thisArg` will be removed in v8. */ export function findIndex( predicate: (this: A, value: T, index: number, source: Observable) => boolean, thisArg: A ): OperatorFunction; export function findIndex(predicate: (value: T, index: number, source: Observable) => boolean): OperatorFunction; /** * Emits only the index of the first value emitted by the source Observable that * meets some condition. * * It's like {@link find}, but emits the index of the * found value, not the value itself. * * ![](findIndex.png) * * `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 * * Emit the index of first click that happens on a DIV element * * ```ts * import { fromEvent, findIndex } from 'rxjs'; * * const div = document.createElement('div'); * div.style.cssText = 'width: 200px; height: 200px; background: #09c;'; * document.body.appendChild(div); * * const clicks = fromEvent(document, 'click'); * const result = clicks.pipe(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 predicate A function called with each item to test for condition matching. * @param thisArg An optional argument to determine the value of `this` in the * `predicate` function. * @return A function that returns an Observable that emits the index of the * first item that matches the condition. */ export function findIndex( predicate: (value: T, index: number, source: Observable) => boolean, thisArg?: any ): OperatorFunction { return operate(createFind(predicate, thisArg, 'index')); }