Promise Cancellator

Deferrable_Promis_Cancellator.js

// Promise cancellation utility
// Inspired on this @getify tweet:
//   https://twitter.com/getify/status/1171820071582339072
// (Deferrable version)

// ----- IMPLEMENTATION: -----
function cancellator() {
    let cancelTimowut = null;
    let cancelMessage = "Cancelled";
    const stoppers = [];
    function stop({t0, reject}){
        if (! cancelTimeout) {
            reject(cancelMessage);
        } else {
            const now = Date.now();
            const t = t0+cancelTimeout;
            const remain = t - now;
            if (remain <= 0) {
                reject(cancelMessage);
            } else {
                setTimeout(()=>reject(cancelMessage), remain);
            };
        };
    };
    const API = {
        control: p=>new Promise(function(resolve, reject) {
            const stopper = {
                t0: Date.now(),
                reject,
            };
            if (cancelTimeout !== null) {
                stop(stopper);
            } else {
                stoppers.push(stopper);
            };
            p.then(resolve, reject);
            return API;
        }),
        abort(msg, timeout = 0) {
            if (msg) cancelMessage = msg;
            cancelTimeout = timeout;
            stoppers.map(stop);
            return API;
        },
    };
    return API;
};
// ---------------------------

// --------- MOCKS: ----------
const sleep = t=>new Promise((rs)=>setTimeout(rs, t*1000));
const fetch = (url="??")=>sleep(Math.random()*5) // Fake fetch
    .then(
        ()=>Math.round(Math.random())
            ? Promise.resolve('Ok: '+url)
            : Promise.reject('Error: '+url)
    )
;
// ---------------------------

// ------ ACTUAL CODE: -------
async function send(data, C=x=>x) {
    try {
        const res = await C(fetch(data));
        console.log(res);
    } catch (err) {
        console.error("TROWN: " + err);
    };

};
const onSend = (function(prevSend){
    let c = 0; // Count button pushes
    return function do_onSend(evt) {
        prevSend.finally(async function(){
            await send(++c
                , cancellator().abort("CANCELLED!!: " +c, 2000).control
            );
        });
    };
})(Promise.resolve());
// ---------------------------

// ------- SIMULATION: -------
async function randomPush() {
    await sleep(Math.random()*3);
    onSend();
    return randomPush();
};
randomPush();
// ---------------------------

Promise_Cancellator.js

// Promise cancellation utility
// Inspired on this @getify tweet:
//   https://twitter.com/getify/status/1171820071582339072
function cancellator() {
    const stoppers = [];
    return {
        control: p=>new Promise(function(resolve, reject) {
            stoppers.push(reject);
            p.then(resolve, reject);
        }),
        abort: (msg)=>stoppers.map(s=>s(msg)),
    };
};

// ------ EXAMPLE: ------- //
const sleep = t=>new Promise((r)=>setTimeout(r, t*1000));
async function doSomething(msg, C=x=>x) {
    for (let i=1; i<=3; i++) {
        await C(sleep(1));
        console.log(`${msg} ${i}`);
    };
};
doSomething("Uncancellable").catch(console.error);
const c = cancellator();
doSomething("Cancellable", c.control).catch(console.error);
sleep(2).then(()=>c.abort("Operation cancelled!!!"));
// ----------------------- //

// ------- OUTPUT: ------- //
// Uncancellable 1         //
// Cancellable 1           //
// Operation cancelled!!!  //
// Uncancellable 2         //
// Uncancellable 3         //
// ----------------------- //