website/node_modules/p-cancelable/readme.md

In JohnCoene/chirp: 'Twitter' Networks Analyser

p-cancelable

Create a promise that can be canceled

Useful for animation, loading resources, long-running async computations, async iteration, etc.

Install

$ npm install --save p-cancelable

Usage

const PCancelable = require('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.

PCancelable.CancelError

Type: Error

Rejection reason when .cancel() is called.

PCancelable.fn(fn)

Convenience method to make your promise-returning or async function cancelable.

The function you specify will have onCancel prepended to its parameters.

const fn = PCancelable.fn((onCancel, input) => {
    const job = new Job();

    onCancel(() => {
        job.cleanup();
    });

    return job.start(); //=> Promise
});

const promise = fn('input'); //=> PCancelable

// …

promise.cancel();

FAQ

Cancelable vs. Cancellable

In American English, the verb cancel is usually inflected canceled and canceling—with one l.Both a browser API and the Cancelable Promises proposal use this spelling.

What about the official Cancelable Promises proposal?

~~It's still an early draft and I don't really like its current direction. It complicates everything and will require deep changes in the ecosystem to adapt to it. And the way you have to use cancel tokens is verbose and convoluted. I much prefer the more pragmatic and less invasive approach in this module.~~ The proposal was withdrawn.

Related

• p-lazy - Create a lazy promise that defers execution until .then() or .catch() is called
• More…

License

MIT © Sindre Sorhus

JohnCoene/chirp documentation built on May 25, 2021, 6:33 p.m.