throwing from callbacks

async.js

// Logs 'rejected Error: sync error'
const p = new Promise((resolve, reject) => {
  throw new Error('sync error');
}).then(null, e => console.log('rejected', e));

// q never settles, uncaught error
const q = new Promise((resolve, reject) => {
  setImmediate(() => { throw new Error('async error'); });
}).then(null, e => console.log('rejected', e));

// r never settles, catch never executes
try {
  const r = new Promise((resolve, reject) => {
    setImmediate(() => { throw new Error('async error'); });
  }).then(null, e => console.log('rejected', e));
} catch (err) {
  console.log('caught', err);
}