@tib/defer

Create a deferred promise

Usage

Promised delay

import {Defer} from '@tib/defer';

function delay(ms) {
  const deferred = new Defer();
  setTimeout(deferred.resolve, ms, '🦄');
  return deferred.promise;
}

(async () => {
  console.log(await delay(100));
  //=> '🦄'
})();

The above is just an example. Use delay if you need to delay a promise.

Testing for callback/event

You can write test cases more elegant with @tib/defer for callback/event testing

class FakeStream extends EventEmitter {
  write(data: any, delays = 10) {
    setTimeout(() => this.emit('data', data), delays);
  }
}
describe('something', () => {
  it('should work with callbacks', async () => {
    const deferred = new Defer();
    const stream = new FakeStream();
    stream.once('data', deferred.resolve);
    stream.write('🦄');
    const data = await deferred;
    expect(data).equal('🦄');
  });
});

API

new Defer()

Returns a promise instance with resolve() and reject() functions.

Related

• Deferred that extends Promise
• p-defer - Create a deferred promise