how could I abort JavaScript Promise?

Question

I am working On NodeJS Project , I used Promise In my code to chain some methods , I needed to abort in one of the 'thens' chain

findEmployeeByCW('11111', "18-09-2016").
then(function () {
    return findEmployeeByCWE('111111', "18-09-2016", '111111')
}, function () {
    console.log('createEmployeeLoginBy')
    createEmployeeLoginBy('111111', "18-09-2016", '111111').
    then(function (log) {
        SaveEmployeeLogToDb(log)
        // ***************
        // ^_^ I need to exit here ....
    })
})
.then(function (log) {
    return updateLoginTimeTo(log, '08-8668', '230993334')
}, function () {
    return createNewEmployeeLog('224314', "18-09-2016",
        '230993334', '08-99')
})
.then(SaveEmployeeLogToDb).then(DisplayLog).catch(function (e) {
    console.log(e);
})

You can store a reference to your promise and then call `reject` on that after `SaveEmployeeLogToDB` — Morteza Tourani, Sep 21 '16 at 19:15
you can just throw an error and the promise will get rejected — Johannes Merz, Sep 21 '16 at 19:35
@mortezaT unfortunately I used that , but it executed the next then's reject — Mohammad Abdullah, Sep 21 '16 at 19:54
Possible duplicate of [How to cancel an EMCAScript6 (vanilla JavaScript) promise chain](http://stackoverflow.com/questions/29478751/how-to-cancel-an-emcascript6-vanilla-javascript-promise-chain) — Dana Cartwright, Sep 21 '16 at 20:15
Possible duplicate of [How to properly break out of a promise chain?](http://stackoverflow.com/q/29499582/1048572) — Bergi, Sep 22 '16 at 01:29
@MohammadAbdullah What exactly do you mean by "exit"? Why not just move all the things that you don't want to do in case of an error into the `success` callback? — Bergi, Sep 22 '16 at 01:29
@Bergi what if i need through coding to abort , should I rebuild the system for single code ??? — Mohammad Abdullah, Sep 22 '16 at 19:37
@MohammadAbdullah Sorry, I don't unserstand what you mean by "single code". But it really sounds like you just want to throw an exception (reject the promises). — Bergi, Sep 22 '16 at 19:44
I mean if i need to exit the code for some reason , should I rebuild my system analysis !! — Mohammad Abdullah, Sep 22 '16 at 21:01

score 2 · Answer 1 · answered Sep 22 '16 at 01:20

If I understand the intention correctly, there is no need here to cancel or throw.

You should be able to achieve your ends by rearrangement :

findEmployeeByCW('11111', "18-09-2016")
.then(function() {
    return findEmployeeByCWE('111111', "18-09-2016", '111111')
    .then(function(log) {
        return updateLoginTimeTo(log, '08-8668', '230993334');
    }, function(e) {
        return createNewEmployeeLog('224314', "18-09-2016", '230993334', '08-99');
    });
}, function(e) {
    return createEmployeeLoginBy('111111', "18-09-2016", '111111');
})
.then(SaveEmployeeLogToDb)
.then(DisplayLog)
.catch(function(e) {
    console.log(e);
});

That should work with the proviso that a log object is always delivered to SaveEmployeeLogToDb via all possible paths to that point, as implied by the original code.

Mr @Roamer-1888 you mean that I should build my system well so that I wan't need the cancellation !!?? maybe it 's a solution but what if i need through coding to abort , should I rebuild the system for single code ?? — Mohammad Abdullah, Sep 22 '16 at 19:23
thanks a lot for your advice Mr @Roamer-1888 , it works for me , I think the main Idea for a Promise is to build the system well , and if an error occurred it should be bubbled to be handled at the tail of the chaining — Mohammad Abdullah, Sep 22 '16 at 19:56

Stas Parshin · Answer 2 · 2016-09-21T20:27:12.517

0

You can't currently "cancel" promises. But you can use an exception for that purpose:

findEmployeeByCW('11111', "18-09-2016").
then(function () {
return findEmployeeByCWE('111111', "18-09-2016", '111111')
}, function () {
console.log('createEmployeeLoginBy')

//*** "return" added
return createEmployeeLoginBy('111111', "18-09-2016", '111111').
then(function (log) {
SaveEmployeeLogToDb(log)

//****
throw new Error('promise_exit');
//****

})
})
.then(function (log) {
return updateLoginTimeTo(log, '08-8668', '230993334')
}, function () {
return createNewEmployeeLog('224314', "18-09-2016",
'230993334', '08-99')
})
.then(SaveEmployeeLogToDb).then(DisplayLog).catch(function (e) {

//****
//Only log if it's not an intended exit
if(e.message != 'promise_exit'){
    console.log(e);
}
//****

})

edited Sep 21 '16 at 20:27

answered Sep 21 '16 at 19:41

Stas Parshin

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I tried before , It didn't work , it continued of execution , I also tried to throw an exception in SaveEmployeeLogToDb method , but it also failed !! – Mohammad Abdullah Sep 21 '16 at 20:01
Try the updated answer. Returning the createEmployeeLoginBy should work. – Stas Parshin Sep 21 '16 at 20:22

how could I abort JavaScript Promise?

2 Answers2