Cancellable Promises

The concept of this kind of cancellable promises was developed for internal usage to make certain things work. The only difference between a native promise and cancellable promise from a client code view is a .cancel method which can be used to reject a promise from the outside world. It still can be passed to native promise methods like Promise.all, Promise.race, etc.

Example usage

import { createCancellablePromise } from 'csp-coffee/cancellablePromise'

const { cancellablePromise, resolve, reject } = createCancellablePromise(() => {
    console.log('Do something when promise is cancelled');
})

createCancellablePromise function accepts an onCancel callback which is called when promise is cancelled. It returns an object with our cancellablePromise and two methods: resolve and reject. resolve and reject act exactly like a resolve and reject inside a promise constructor and provide a way to control a promise from the outside. Value inside of a cancellablePromise property contains our promise with a .cancel method.

Cancelling the promise

cancel: (reason?: any) => Promise<void>

.cancel accepts any value as an argument and this is a value the onCancel callback will be called with. It returns a promise which resolves once cancellation is done

import { createCancellablePromise } from 'csp-coffee/cancellablePromise'

const { cancellablePromise, resolve, reject } = createCancellablePromise((message: string) => {
    console.log(message);
});

cancellablePromise.cancel('I AM CANCELLED')

// Will log 'I AM CANCELLED' to the console