CancelablePromise

Promise that can be canceled, learned from sindresorhus/p-cancelable.

The difference from sindresorhus version is that CancelablePromise in this lib is not a subclass of Promise.

Install

$ npm i @ybq/p-cancelable

Usage

const PCancelable = require('@ybq/p-cancelable');

const cancelablePromise = new PCancelable((onCancel, resolve, reject) => {
    const worker = new SomeLongRunningOperation();

    onCancel(() => {
        worker.close();
    });

    worker.on('finish', resolve);
    worker.on('error', reject);
});

cancelablePromise
    .then(value => {
        console.log('Operation finished successfully:', value);
    })
    .catch(reason => {
        if (cancelablePromise.canceled) {
            // Handle the cancelation here
            console.log('Operation was canceled');
            return;
        }

        throw reason;
    });

// Cancel the operation after 10 seconds
setTimeout(() => {
    cancelablePromise.cancel();
}, 10000);

API

new PCancelable(executor)

Same as the Promise constructor, but with a prepended onCancel parameter in executor.

PCancelable is a subclass of Promise.

onCanceled(fn)

Type: Function

Accepts a function that is called when the promise is canceled.

You're not required to call this function.

PCancelable#cancel()

Type: Function

Cancel the promise. The cancellation is synchronous.

Calling it after the promise has settled or multiple times does nothing.

PCancelable#canceled

Type: boolean

Whether the promise is canceled.