Limiting promises

limitedPromises.ts

import * as promiseLimit from "promise-limit";

function getRandomInt(min, max) {
    return Math.floor(Math.random() * (max - min + 1)) + min;
}

function log(value: any) {
    // tslint:disable-next-line:no-console
    console.log(`>> ${value}`);
}

function longUnreliableTask(value: number) {
    return new Promise<number>((resolve, reject) => {
        const timeoutSecs = getRandomInt(1, 3) * 1000;
        log(`starting job ${value} for ${timeoutSecs} ms`);
        setTimeout(() => {
            log(`job ${timeoutSecs} done`);
            if (getRandomInt(1, 5) === 1) {
                reject("FAIL");
            } else {
                resolve(value * value);
            }
        }, timeoutSecs);
    });
}

async function longReliableTask(value: number) {
    try {
        return await longUnreliableTask(value);
    } catch (error) {
        log(error);
        return null;
    }
}

(async () => {
    log("start");

    const input = [1, 2, 3, 4, 5, 6, 7, 8, 9];
    // const promises = input.map(longReliableTask); // usual promises

    const limitFunc = promiseLimit(2);
    const limitedPromises = input.map((name) => limitFunc(() => longReliableTask(name)));

    const results = await Promise.all(limitedPromises);
    log(`results: ${JSON.stringify(results)}`);
    log("end");
})();