@reactivex/rxjs/dist/es6/operator/takeLast.js

Reactive Extensions for modern JavaScript

import { Subscriber } from '../Subscriber';
import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
import { EmptyObservable } from '../observable/EmptyObservable';
/**
 * @throws {ArgumentOutOfRangeError} When using `takeLast(i)`, it delivers an
 * ArgumentOutOrRangeError to the Observer's `error` callback if `i < 0`.
 * @param total
 * @return {any}
 * @method takeLast
 * @owner Observable
 */
export function takeLast(total) {
    if (total === 0) {
        return new EmptyObservable();
    }
    else {
        return this.lift(new TakeLastOperator(total));
    }
}
class TakeLastOperator {
    constructor(total) {
        this.total = total;
        if (this.total < 0) {
            throw new ArgumentOutOfRangeError;
        }
    }
    call(subscriber, source) {
        return source._subscribe(new TakeLastSubscriber(subscriber, this.total));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class TakeLastSubscriber extends Subscriber {
    constructor(destination, total) {
        super(destination);
        this.total = total;
        this.ring = new Array();
        this.count = 0;
    }
    _next(value) {
        const ring = this.ring;
        const total = this.total;
        const count = this.count++;
        if (ring.length < total) {
            ring.push(value);
        }
        else {
            const index = count % total;
            ring[index] = value;
        }
    }
    _complete() {
        const destination = this.destination;
        let count = this.count;
        if (count > 0) {
            const total = this.count >= this.total ? this.total : this.count;
            const ring = this.ring;
            for (let i = 0; i < total; i++) {
                const idx = (count++) % total;
                destination.next(ring[idx]);
            }
        }
        destination.complete();
    }
}
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