| import { Subscriber } from '../Subscriber'; |
| import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError'; |
| /** |
| * Skip the last `count` values emitted by the source Observable. |
| * |
| * <img src="./img/skipLast.png" width="100%"> |
| * |
| * `skipLast` returns an Observable that accumulates a queue with a length |
| * enough to store the first `count` values. As more values are received, |
| * values are taken from the front of the queue and produced on the result |
| * sequence. This causes values to be delayed. |
| * |
| * @example <caption>Skip the last 2 values of an Observable with many values</caption> |
| * var many = Rx.Observable.range(1, 5); |
| * var skipLastTwo = many.skipLast(2); |
| * skipLastTwo.subscribe(x => console.log(x)); |
| * |
| * // Results in: |
| * // 1 2 3 |
| * |
| * @see {@link skip} |
| * @see {@link skipUntil} |
| * @see {@link skipWhile} |
| * @see {@link take} |
| * |
| * @throws {ArgumentOutOfRangeError} When using `skipLast(i)`, it throws |
| * ArgumentOutOrRangeError if `i < 0`. |
| * |
| * @param {number} count Number of elements to skip from the end of the source Observable. |
| * @returns {Observable<T>} An Observable that skips the last count values |
| * emitted by the source Observable. |
| * @method skipLast |
| * @owner Observable |
| */ |
| export function skipLast(count) { |
| return (source) => source.lift(new SkipLastOperator(count)); |
| } |
| class SkipLastOperator { |
| constructor(_skipCount) { |
| this._skipCount = _skipCount; |
| if (this._skipCount < 0) { |
| throw new ArgumentOutOfRangeError; |
| } |
| } |
| call(subscriber, source) { |
| if (this._skipCount === 0) { |
| // If we don't want to skip any values then just subscribe |
| // to Subscriber without any further logic. |
| return source.subscribe(new Subscriber(subscriber)); |
| } |
| else { |
| return source.subscribe(new SkipLastSubscriber(subscriber, this._skipCount)); |
| } |
| } |
| } |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class SkipLastSubscriber extends Subscriber { |
| constructor(destination, _skipCount) { |
| super(destination); |
| this._skipCount = _skipCount; |
| this._count = 0; |
| this._ring = new Array(_skipCount); |
| } |
| _next(value) { |
| const skipCount = this._skipCount; |
| const count = this._count++; |
| if (count < skipCount) { |
| this._ring[count] = value; |
| } |
| else { |
| const currentIndex = count % skipCount; |
| const ring = this._ring; |
| const oldValue = ring[currentIndex]; |
| ring[currentIndex] = value; |
| this.destination.next(oldValue); |
| } |
| } |
| } |
| //# sourceMappingURL=skipLast.js.map |