loop-controls/dist/concurrent.js

break/continue controls for loops and higher-order functions (sync, async, concurrent). Designed to compose with ts-pattern.

import { _Break, _Continue } from "./core.js";
export async function forEachConcurrent(items, fn, { concurrency } = {}) {
    if (concurrency !== undefined && concurrency < 1)
        concurrency = 1;
    const c = new AbortController();
    const { signal } = c;
    let broken = false;
    let index = 0;
    const ctrl = {
        signal,
        continue: () => { throw new _Continue(); },
        break: (value) => { c.abort(); throw new _Break(value); },
    };
    const worker = async () => {
        while (!signal.aborted) {
            const i = index++;
            if (i >= items.length)
                return;
            const item = items[i];
            try {
                await fn(item, ctrl, i);
            }
            catch (e) {
                if (e instanceof _Continue)
                    continue;
                if (e instanceof _Break) {
                    broken = true;
                    return;
                }
                c.abort();
                throw e;
            }
        }
    };
    const workerCount = concurrency ?? items.length;
    const workers = Array.from({ length: workerCount }, () => worker());
    try {
        await Promise.all(workers);
    }
    catch (e) {
        if (!(e instanceof _Break) && !(e instanceof _Continue))
            throw e;
        broken = true;
    }
    return { broken };
}
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