sindresorhus

p-cancelable

		super(reason || 'Promise was canceled');

			return new PCancelable((resolve, reject, onCancel) => {

				userFn(...args).then(resolve, reject);

		this._promise = new Promise((resolve, reject) => {

			return executor(onResolve, onReject, onCancel);

		return this._promise.then(onFulfilled, onRejected);

		return this._promise.catch(onRejected);

		return this._promise.finally(onFinally);

		if (!this._isPending || this._isCanceled) {

				for (const handler of this._cancelHandlers) {

			this._reject(new CancelError(reason));

Object.setPrototypeOf(PCancelable.prototype, Promise.prototype);

module.exports.CancelError = CancelError;

	"description": "Create a promise that can be canceled",

	"repository": "sindresorhus/p-cancelable",

# p-cancelable [![Build Status](https://travis-ci.org/sindresorhus/p-cancelable.svg?branch=master)](https://travis-ci.org/sindresorhus/p-cancelable)

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

const PCancelable = require('p-cancelable');

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

	const worker = new SomeLongRunningOperation();

		console.log('Operation finished successfully:', await cancelablePromise);

			console.log('Operation was canceled');

	cancelablePromise.cancel('Unicorn has changed its color');

Same as the [`Promise` constructor](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise), but with an appended `onCancel` parameter in `executor`.

Same as the [`Promise` constructor](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise), but with an appended `onCancel` parameter in `executor`.<br>

Cancelling will reject the promise with `PCancelable.CancelError`. To avoid that, set `onCancel.shouldReject` to `false`.

const cancelable = new PCancelable((resolve, reject, onCancel) => {

promise.cancel(); // Doesn't throw an error

`PCancelable` is a subclass of `Promise`.

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

You're not required to call this function. You can call this function multiple times to add multiple cancel handlers.

Cancel the promise and optionally provide a reason.

The cancellation is synchronous. Calling it after the promise has settled or multiple times does nothing.

Rejection reason when `.cancel()` is called.

It includes a `.isCanceled` property for convenience.

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

The function you specify will have `onCancel` appended to its parameters.

const fn = PCancelable.fn((input, onCancel) => {

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

[In American English, the verb cancel is usually inflected canceled and canceling—with one l.](http://grammarist.com/spelling/cancel/)<br>Both a [browser API](https://developer.mozilla.org/en-US/docs/Web/API/Event/cancelable) and the [Cancelable Promises proposal](https://github.com/tc39/proposal-cancelable-promises) use this spelling.

### What about the official [Cancelable Promises proposal](https://github.com/tc39/proposal-cancelable-promises)?

~~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.

- [p-progress](https://github.com/sindresorhus/p-progress) - Create a promise that reports progress

- [p-lazy](https://github.com/sindresorhus/p-lazy) - Create a lazy promise that defers execution until `.then()` or `.catch()` is called

- [More…](https://github.com/sindresorhus/promise-fun)

		@@ -28,2 +28,3 @@ 'use strict';
		this._isCanceled = false;
		this._rejectOnCancel = true;

		@@ -33,15 +34,26 @@ this._promise = new Promise((resolve, reject) => {

		return executor(
		value => {
		this._isPending = false;
		resolve(value);
		},
		error => {
		this._isPending = false;
		reject(error);
		},
		handler => {
		this._cancelHandlers.push(handler);
		const onResolve = value => {
		this._isPending = false;
		resolve(value);
		};

		const onReject = error => {
		this._isPending = false;
		reject(error);
		};

		const onCancel = handler => {
		this._cancelHandlers.push(handler);
		};

		Object.defineProperties(onCancel, {
		shouldReject: {
		get: () => this._rejectOnCancel,
		set: bool => {
		this._rejectOnCancel = bool;
		}
		}
		);
		});

		return executor(onResolve, onReject, onCancel);
		});
		@@ -78,3 +90,5 @@ }
		this._isCanceled = true;
		this._reject(new CancelError(reason));
		if (this._rejectOnCancel) {
		this._reject(new CancelError(reason));
		}
		}
		@@ -81,0 +95,0 @@

		{
		"name": "p-cancelable",
		"version": "0.5.0",
		"version": "0.5.1",
		"description": "Create a promise that can be canceled",
		@@ -45,4 +45,4 @@ "license": "MIT",
		"promise.prototype.finally": "^3.1.0",
		"xo": "*"
		"xo": "^0.23.0"
		}
		}

		@@ -56,4 +56,20 @@ # p-cancelable [![Build Status](https://travis-ci.org/sindresorhus/p-cancelable.svg?branch=master)](https://travis-ci.org/sindresorhus/p-cancelable)

		Same as the [`Promise` constructor](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise), but with an appended `onCancel` parameter in `executor`.
		Same as the [`Promise` constructor](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise), but with an appended `onCancel` parameter in `executor`.<br>
		Cancelling will reject the promise with `PCancelable.CancelError`. To avoid that, set `onCancel.shouldReject` to `false`.

		```js
		const cancelable = new PCancelable((resolve, reject, onCancel) => {
		const job = new Job();

		onCancel.shouldReject = false;
		onCancel(() => {
		job.stop();
		});

		job.on('finish', resolve);
		});

		promise.cancel(); // Doesn't throw an error
		```

		`PCancelable` is a subclass of `Promise`.
		@@ -60,0 +76,0 @@

Improved metrics