import { first as higherOrder } from '../operators/first'; /** * Emits only the first value (or the first value that meets some condition) * emitted by the source Observable. * * Emits only the first value. Or emits only the first * value that passes some test. * * * * If called with no arguments, `first` emits the first value of the source * Observable, then completes. If called with a `predicate` function, `first` * emits the first value of the source that matches the specified condition. It * may also take a `resultSelector` function to produce the output value from * the input value, and a `defaultValue` to emit in case the source completes * before it is able to emit a valid value. Throws an error if `defaultValue` * was not provided and a matching element is not found. * * @example Emit only the first click that happens on the DOM * var clicks = Rx.Observable.fromEvent(document, 'click'); * var result = clicks.first(); * result.subscribe(x => console.log(x)); * * @example Emits the first click that happens on a DIV * var clicks = Rx.Observable.fromEvent(document, 'click'); * var result = clicks.first(ev => ev.target.tagName === 'DIV'); * result.subscribe(x => console.log(x)); * * @see {@link filter} * @see {@link find} * @see {@link take} * * @throws {EmptyError} Delivers an EmptyError to the Observer's `error` * callback if the Observable completes before any `next` notification was sent. * * @param {function(value: T, index: number, source: Observable): boolean} [predicate] * An optional function called with each item to test for condition matching. * @param {function(value: T, index: number): R} [resultSelector] A function to * produce the value on the output Observable based on the values * and the indices of the source Observable. The arguments passed to this * function are: * - `value`: the value that was emitted on the source. * - `index`: the "index" of the value from the source. * @param {R} [defaultValue] The default value emitted in case no valid value * was found on the source. * @return {Observable} An Observable of the first item that matches the * condition. * @method first * @owner Observable */ export function first(predicate, resultSelector, defaultValue) { return higherOrder(predicate, resultSelector, defaultValue)(this); } //# sourceMappingURL=first.js.map