Explore when to throw vs reject

promises-async-await.js

function asyncWork(options) {
  let opt = options || {};

  return new Promise((resolve, reject) => {
    setTimeout(() => {
      if (opt.error) {
        const e = new Error(`An error has occured in "work ${opt.name}"`);
        e.name = 'MyError';

        // ERROR: throw is not caught by enclosing try catch
        // throw e;

        // Success: reject is caught by enclosing try catch
        return reject(e);
      }
      resolve(opt.name);
    }, opt.delay || 10);
  });
}

async function main() {
  // return Promise.reject(new Error('simulate unhandled promise rejection'));

  try {
    const result1 = await asyncWork({ name: 'one', delay: 1000 });
    console.log(result1);

    const result2 = await asyncWork({ name: 'two' });
    console.log(result2);

    // Success: this error is caught by try catch
    // throw new Error('Success, error caught');

    const result3 = await asyncWork({ name: 'three', error: true });
    console.log(result3);
  } catch(e) {
    console.log(`Caught ${e.name}, message: ${e.message}`);
  }
}

// hopefully this never gets invoked
process.on('uncaughtException', (e) => {
  console.log('*** Error not caught');
});

// hopefully this never gets invoked
process.on('unhandledRejection', (e) => {
  console.log('*** Promise rejection not caught');
});

main();