How to cancel a promise in javascript?

Question

var promise1 = new Promise(function(resolve, reject) { 
       // ajax api call
});
var promise2 = new Promise(function(resolve, reject) { 
       // ajax api call
});

I want to be able to do something like -

if(a < b) {
  promise1.cancel();
}

Promises are not cancellable. [The proposal](https://github.com/tc39/proposal-cancelable-promises) to add this functionality was withdrawn because of opposition from Google. — Felix Kling, Jan 10 '17 at 07:13
Take a look at this question - http://stackoverflow.com/questions/29478751/how-to-cancel-an-emcascript6-vanilla-javascript-promise-chain — Ajay Narain Mathur, Jan 10 '17 at 07:15
Take a look here : http://stackoverflow.com/questions/30233302/promise-is-it-possible-to-force-cancel-a-promise — Mihai Alexandru-Ionut, Jan 10 '17 at 07:16
Promises are not cancellable refer to this [Link](http://stackoverflow.com/questions/30233302/promise-is-it-possible-to-force-cancel-a-promise) — Saurabh Agrawal, Jan 10 '17 at 07:18
There are still discussions around this though, you might want to search on https://esdiscuss.org/ . — Felix Kling, Jan 10 '17 at 07:21
Perhaps describe what problem you're really trying to solve and folks here could help you solve it with a supported set of functionality. — jfriend00, Jan 10 '17 at 10:15

score 8 · Answer 1 · answered Jan 12 '17 at 20:07

You can't cancel a Promise, but you can chain your promises with then, and reject at any point.

new Promise((resolve, reject) => {
    // step 1
})
.then((result) => {
    if (!result) {
        // Reject the promise chain
        throw 'cancel';
    } else {
        return ... // step 2
    }
})
.catch(err => {
    // cancelled
});

How to cancel a promise in javascript?

1 Answers1