A JavaScript library that provides primitives for creating cancelable asynchronous operations.
Install using npm:
npm install cancel
import Cancellation, { CancellationError } from 'cancel';
// This is an example of a simple HTTP client that supports cancellation.
// The `sendRequest` method sends an HTTP request asynchronously.
// It takes a `Cancellation` object as one of its parameters.
function sendRequest(method, url, body, cancellation) {
// Check if cancellation has already been requested
if (cancellation.isCanceled()) {
// Reject with `CancellationError` so that the caller can distinguish between cancellation and failure
return Promise.reject(new CancellationError('Request has been canceled.'));
};
return new Promise(function executor(resolve, reject) {
const request = new XMLHttpRequest();
request.open(method, url, true);
request.onload = () => resolve({
status: request.status,
body: request.response,
});
request.onerror = () => reject(new Error('A network error has occurred.'));
// Add a listener that will be called when cancellation is requested
cancellation.onCancel(() => {
// Abort the HTTP request
request.abort();
// Reject with `CancellationError` so that the caller can distinguish between cancellation and failure
reject(new CancellationError('Request has been canceled.'));
});
request.send(body);
});
}
// Create a new `Cancellation` object
const cancellation = new Cancellation();
// Pass the `Cancellation` object to the `sendRequest` method
sendRequest('GET', 'https://api.github.com/users/nickuraltsev/starred', null, cancellation)
.then(response => console.log(`Response status: ${response.status}`))
.catch(error => {
if (error instanceof CancellationError) {
console.log('Request canceled');
} else {
console.log('Network failure');
}
});
// ...
// Cancel the request
cancellation.cancel();Creates a new Cancellation object.
Issues a cancellation request.
It is safe to call this method multiple times since all but the first call are ignored.
Returns true if cancellation has been requested; otherwise, returns false.
Adds a listener to be notified when cancellation is requested.
listener- A function to be called when cancellation is requested.
Returns a function that, when called, removes the listener.
Throws a CancellationError if cancellation has been requested.
Creates a child Cancellation object that will be canceled when the parent object is canceled.
Contains a Cancellation object that is already in the canceled state.
The error that is thrown when an operation is canceled.
Creates a new instance of CancellationError.
message- The error message.
Prior to the release 1.0, minor versions may introduce breaking changes.