@reactivex/ix-esnext-esm/asynciterable/operators/scan.js

The Interactive Extensions for JavaScript

import { AsyncIterableX } from '../asynciterablex';
export class ScanAsyncIterable extends AsyncIterableX {
    constructor(source, fn, seed) {
        super();
        this._source = source;
        this._fn = fn;
        this._hasSeed = seed.length === 1;
        this._seed = seed[0];
    }
    async *[Symbol.asyncIterator]() {
        let i = 0;
        let hasValue = false;
        let acc = this._seed;
        for await (const item of this._source) {
            if (hasValue || (hasValue = this._hasSeed)) {
                acc = await this._fn(acc, item, i++);
                yield acc;
            }
            else {
                acc = item;
                hasValue = true;
                i++;
            }
        }
        if (i === 1 && !this._hasSeed) {
            yield acc;
        }
    }
}
export function scan(accumulator, ...seed) {
    return function scanOperatorFunction(source) {
        return new ScanAsyncIterable(source, accumulator, seed);
    };
}

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