@reactivex/ix-esnext-esm/asynciterable/combinelatest.js

The Interactive Extensions for JavaScript

import { AsyncIterableX } from './asynciterablex';
import { identity, identityAsync } from '../util/identity';
// eslint-disable-next-line @typescript-eslint/no-empty-function
const NEVER_PROMISE = new Promise(() => { });
function wrapPromiseWithIndex(promise, index) {
    return promise.then(value => ({ value, index }));
}
export class CombineLatestAsyncIterable extends AsyncIterableX {
    constructor(sources, fn) {
        super();
        this._sources = sources;
        this._fn = fn;
    }
    async *[Symbol.asyncIterator]() {
        const fn = this._fn;
        const length = this._sources.length;
        const iterators = new Array(length);
        const nexts = new Array(length);
        let hasValueAll = false;
        const values = new Array(length);
        const hasValues = new Array(length);
        let active = length;
        hasValues.fill(false);
        for (let i = 0; i < length; i++) {
            const iterator = this._sources[i][Symbol.asyncIterator]();
            iterators[i] = iterator;
            nexts[i] = wrapPromiseWithIndex(iterator.next(), i);
        }
        while (active > 0) {
            const next = Promise.race(nexts);
            const { value: next$, index } = await next;
            if (next$.done) {
                nexts[index] = NEVER_PROMISE;
                active--;
            }
            else {
                values[index] = next$.value;
                hasValues[index] = true;
                const iterator$ = iterators[index];
                nexts[index] = wrapPromiseWithIndex(iterator$.next(), index);
                if (hasValueAll || (hasValueAll = hasValues.every(identity))) {
                    yield await fn(values);
                }
            }
        }
    }
}
export function combineLatest(...sources) {
    let fn = (sources.shift() || identityAsync);
    if (fn && typeof fn !== 'function') {
        sources.unshift(fn);
        fn = identityAsync;
    }
    return new CombineLatestAsyncIterable(sources, fn);
}

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