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feat(takeLast): adds takeLast operator.
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‎perf/micro/current-thread-scheduler/operators/takelast.js

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var RxOld = require('rx');
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var RxNew = require('../../../../index');
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module.exports = function (suite) {
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var oldTakeLastWithImmediateScheduler = RxOld.Observable.range(0, 500, RxOld.Scheduler.currentThread).takeLast(50);
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var newTakeLastWithImmediateScheduler = RxNew.Observable.range(0, 500, RxNew.Scheduler.queue).takeLast(50);
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function _next(x) { }
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function _error(e) { }
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function _complete() { }
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return suite
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.add('old take with immediate scheduler', function () {
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oldTakeLastWithImmediateScheduler.subscribe(_next, _error, _complete);
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})
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.add('new take with immediate scheduler', function () {
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newTakeLastWithImmediateScheduler.subscribe(_next, _error, _complete);
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});
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};

‎perf/micro/immediate-scheduler/operators/takelast.js

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var RxOld = require('rx');
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var RxNew = require('../../../../index');
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module.exports = function (suite) {
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var oldTakeLastWithImmediateScheduler = RxOld.Observable.range(0, 500, RxOld.Scheduler.immediate).takeLast(50);
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var newTakeLastWithImmediateScheduler = RxNew.Observable.range(0, 500).takeLast(50);
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function _next(x) { }
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function _error(e) { }
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function _complete() { }
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return suite
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.add('old take with immediate scheduler', function () {
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oldTakeLastWithImmediateScheduler.subscribe(_next, _error, _complete);
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})
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.add('new take with immediate scheduler', function () {
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newTakeLastWithImmediateScheduler.subscribe(_next, _error, _complete);
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});
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};

‎spec/operators/takeLast-spec.js

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/* globals describe, it, expect, expectObservable, expectSubscriptions, cold, hot */
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var Rx = require('../../dist/cjs/Rx');
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var Observable = Rx.Observable;
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describe('Observable.prototype.takeLast()', function () {
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it.asDiagram('takeLast(2)')('should take two values of an observable with many values', function () {
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var e1 = cold('--a-----b----c---d--| ');
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var e1subs = '^ ! ';
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var expected = '--------------------(cd|)';
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expectObservable(e1.takeLast(2)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should work with empty', function () {
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var e1 = cold('|');
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var e1subs = '(^!)';
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var expected = '|';
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expectObservable(e1.takeLast(42)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should go on forever on never', function () {
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var e1 = cold('-');
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var e1subs = '^';
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var expected = '-';
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expectObservable(e1.takeLast(42)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should be empty on takeLast(0)', function () {
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var e1 = hot('--a--^--b----c---d--|');
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var e1subs = []; // Don't subscribe at all
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var expected = '|';
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expectObservable(e1.takeLast(0)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should take one value from an observable with one value', function () {
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var e1 = hot('---(a|)');
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var e1subs = '^ ! ';
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var expected = '---(a|)';
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expectObservable(e1.takeLast(1)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should take one value from an observable with many values', function () {
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var e1 = hot('--a--^--b----c---d--| ');
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var e1subs = '^ ! ';
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var expected = '---------------(d|)';
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expectObservable(e1.takeLast(1)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should error on empty', function () {
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var e1 = hot('--a--^----|');
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var e1subs = '^ !';
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var expected = '-----|';
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expectObservable(e1.takeLast(42)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should propagate error from the source observable', function () {
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var e1 = hot('---^---#', null, 'too bad');
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var e1subs = '^ !';
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var expected = '----#';
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expectObservable(e1.takeLast(42)).toBe(expected, null, 'too bad');
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should propagate error from an observable with values', function () {
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var e1 = hot('---^--a--b--#');
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var e1subs = '^ !';
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var expected = '---------#';
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expectObservable(e1.takeLast(42)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should allow unsubscribing explicitly and early', function () {
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var e1 = hot('---^--a--b-----c--d--e--|');
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var unsub = ' ! ';
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var e1subs = '^ ! ';
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var expected = '---------- ';
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expectObservable(e1.takeLast(42), unsub).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should work with throw', function () {
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var e1 = cold('#');
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var e1subs = '(^!)';
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var expected = '#';
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expectObservable(e1.takeLast(42)).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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it('should throw if total is less than zero', function () {
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expect(function () { Observable.range(0,10).takeLast(-1); })
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.toThrow(new Rx.ArgumentOutOfRangeError());
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});
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it('should not break unsubscription chain when unsubscribed explicitly', function () {
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var e1 = hot('---^--a--b-----c--d--e--|');
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var unsub = ' ! ';
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var e1subs = '^ ! ';
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var expected = '---------- ';
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var result = e1
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.mergeMap(function (x) { return Observable.of(x); })
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.takeLast(42)
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.mergeMap(function (x) { return Observable.of(x); });
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expectObservable(result, unsub).toBe(expected);
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expectSubscriptions(e1.subscriptions).toBe(e1subs);
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});
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});

‎src/CoreOperators.ts

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switchMap?: <R>(project: ((x: T, ix: number) => Observable<any>), projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
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switchMapTo?: <R>(observable: Observable<any>, projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
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take?: (count: number) => Observable<T>;
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takeLast?: (count: number) => Observable<T>;
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takeUntil?: (notifier: Observable<any>) => Observable<T>;
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takeWhile?: (predicate: (value: T, index: number) => boolean) => Observable<T>;
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throttle?: (durationSelector: (value: T) => Observable<any> | Promise<any>) => Observable<T>;

‎src/Observable.ts

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switchMap: <R>(project: ((x: T, ix: number) => Observable<any>), projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
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switchMapTo: <R>(observable: Observable<any>, projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
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take: (count: number) => Observable<T>;
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takeLast: (count: number) => Observable<T>;
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takeUntil: (notifier: Observable<any>) => Observable<T>;
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takeWhile: (predicate: (value: T, index: number) => boolean) => Observable<T>;
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throttle: (durationSelector: (value: T) => Observable<any> | Promise<any>) => Observable<T>;

‎src/Rx.DOM.ts

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import './add/operator/switchMap';
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import './add/operator/switchMapTo';
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import './add/operator/take';
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import './add/operator/takeLast';
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import './add/operator/takeUntil';
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import './add/operator/takeWhile';
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import './add/operator/throttle';

‎src/Rx.KitchenSink.ts

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import './add/operator/switchMap';
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import './add/operator/switchMapTo';
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import './add/operator/take';
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import './add/operator/takeLast';
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import './add/operator/takeUntil';
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import './add/operator/takeWhile';
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import './add/operator/throttle';

‎src/Rx.ts

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import './add/operator/switchMap';
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import './add/operator/switchMapTo';
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import './add/operator/take';
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import './add/operator/takeLast';
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import './add/operator/takeUntil';
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import './add/operator/takeWhile';
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import './add/operator/throttle';

‎src/add/operator/takeLast.ts

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/**
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* Everything in this file is generated by the 'tools/generate-operator-patches.ts' script.
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* Any manual edits to this file will be lost next time the script is run.
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**/
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import {Observable} from '../../Observable';
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import {takeLast} from '../../operator/takeLast';
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Observable.prototype.takeLast = takeLast;
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export var _void: void;

‎src/operator/takeLast.ts

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import {Operator} from '../Operator';
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import {Subscriber} from '../Subscriber';
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import {ArgumentOutOfRangeError} from '../util/ArgumentOutOfRangeError';
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import {EmptyObservable} from '../observable/empty';
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import {Observable} from '../Observable';
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export function takeLast<T>(total: number): Observable<T> {
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if (total === 0) {
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return new EmptyObservable<T>();
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} else {
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return this.lift(new TakeLastOperator(total));
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}
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}
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class TakeLastOperator<T> implements Operator<T, T> {
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constructor(private total: number) {
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if (this.total < 0) {
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throw new ArgumentOutOfRangeError;
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}
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}
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call(subscriber: Subscriber<T>): Subscriber<T> {
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return new TakeLastSubscriber(subscriber, this.total);
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}
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}
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class TakeLastSubscriber<T> extends Subscriber<T> {
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private ring: T[];
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private count: number = 0;
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private index: number = 0;
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constructor(destination: Subscriber<T>, private total: number) {
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super(destination);
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this.ring = new Array(total);
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}
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protected _next(value: T): void {
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let index = this.index;
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const ring = this.ring;
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const total = this.total;
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const count = this.count;
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if (total > 1) {
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if (count < total) {
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this.count = count + 1;
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this.index = index + 1;
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} else if (index === 0) {
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this.index = ++index;
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} else if (index < total) {
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this.index = index + 1;
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} else {
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this.index = index = 0;
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}
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} else if (count < total) {
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this.count = total;
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}
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ring[index] = value;
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}
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protected _complete(): void {
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let iter = -1;
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const { ring, count, total, destination } = this;
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let index = (total === 1 || count < total) ? 0 : this.index - 1;
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while (++iter < count) {
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if (iter + index === total) {
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index = total - iter;
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}
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destination.next(ring[iter + index]);
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}
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destination.complete();
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}
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}

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