only-last-promise - Resolve or reject only last Promise

only-last-promise

Resolve or reject only last Promise.

Useful if you want to "abort" already running async operations started with debounced input event.

Install

npm install only-last-promise --save

Usage

When calling the wrapper function multiple times, only the last returned Promise will resolve or reject and all other Promise s will be aborted with DiscardSignal error.

In the following example, fetch requests for /buddy and /allie will be discarded (they will return undefined ), and only /becky will be resolved with Response .

import onlyLastPromise, { DiscardSignal } from 'only-last-promise';

const wrapper = onlyLastPromise();

const wrappedFetch = async (url) => {
	try {
		return await wrapper(fetch(url));
	} catch (error) {
		if (!(error instanceof DiscardSignal)) {
			throw error;
		}
	}
};

(async () => {
	await Promise.all([
		wrappedFetch('/buddy'),
		wrappedFetch('/allie'),
		wrappedFetch('/becky')
	]);
	// => [undefined, undefined, Response]
})();

API

onlyLastPromise()

Returns: Function

Factory function which returns wrapper function.

wrapper(promise)

Type: Function

promise

Type: Promise

Promise to handle.

Browser support

Tested in IE9+ and all modern browsers, assuming Promise is available.

Test

For automated tests, run npm run test:automated (append :watch for watcher support).

License

MIT © Ivan Nikolić