@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
117 lines • 4.39 kB
JavaScript
;
var __extends = (this && this.__extends) || (function () {
var extendStatics = function (d, b) {
extendStatics = Object.setPrototypeOf ||
({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
return extendStatics(d, b);
}
return function (d, b) {
extendStatics(d, b);
function __() { this.constructor = d; }
d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
})();
Object.defineProperty(exports, "__esModule", { value: true });
var Subscriber_1 = require("../Subscriber");
/**
* Emits only the first value emitted by the source Observable that meets some
* condition.
*
* <span class="informal">Finds the first value that passes some test and emits
* that.</span>
*
* 
*
* `find` searches for the first item in the source Observable that matches the
* specified condition embodied by the `predicate`, and returns the first
* occurrence in the source. Unlike {@link first}, the `predicate` is required
* in `find`, and does not emit an error if a valid value is not found.
*
* ## Example
* Find and emit the first click that happens on a DIV element
* ```ts
* import { fromEvent } from 'rxjs';
* import { find } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(find(ev => ev.target.tagName === 'DIV'));
* result.subscribe(x => console.log(x));
* ```
*
* @see {@link filter}
* @see {@link first}
* @see {@link findIndex}
* @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<T>} An Observable of the first item that matches the
* condition.
* @method find
* @owner Observable
*/
function find(predicate, thisArg) {
if (typeof predicate !== 'function') {
throw new TypeError('predicate is not a function');
}
return function (source) { return source.lift(new FindValueOperator(predicate, source, false, thisArg)); };
}
exports.find = find;
var FindValueOperator = /** @class */ (function () {
function FindValueOperator(predicate, source, yieldIndex, thisArg) {
this.predicate = predicate;
this.source = source;
this.yieldIndex = yieldIndex;
this.thisArg = thisArg;
}
FindValueOperator.prototype.call = function (observer, source) {
return source.subscribe(new FindValueSubscriber(observer, this.predicate, this.source, this.yieldIndex, this.thisArg));
};
return FindValueOperator;
}());
exports.FindValueOperator = FindValueOperator;
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
var FindValueSubscriber = /** @class */ (function (_super) {
__extends(FindValueSubscriber, _super);
function FindValueSubscriber(destination, predicate, source, yieldIndex, thisArg) {
var _this = _super.call(this, destination) || this;
_this.predicate = predicate;
_this.source = source;
_this.yieldIndex = yieldIndex;
_this.thisArg = thisArg;
_this.index = 0;
return _this;
}
FindValueSubscriber.prototype.notifyComplete = function (value) {
var destination = this.destination;
destination.next(value);
destination.complete();
this.unsubscribe();
};
FindValueSubscriber.prototype._next = function (value) {
var _a = this, predicate = _a.predicate, thisArg = _a.thisArg;
var index = this.index++;
try {
var result = predicate.call(thisArg || this, value, index, this.source);
if (result) {
this.notifyComplete(this.yieldIndex ? index : value);
}
}
catch (err) {
this.destination.error(err);
}
};
FindValueSubscriber.prototype._complete = function () {
this.notifyComplete(this.yieldIndex ? -1 : undefined);
};
return FindValueSubscriber;
}(Subscriber_1.Subscriber));
exports.FindValueSubscriber = FindValueSubscriber;
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