async/await error scenarios and variations

index.js

/* eslint no-console: 0 */
/* eslint no-unused-vars: 0 */
const https = require('https');

const goodUrl = 'https://jsonplaceholder.typicode.com/users/1';
const badUrl = 'https://jsonplaceholder.typicode.com/foo';
const badDomain = 'https://no.such.url';

const externalCall = (url, t = 0) => new Promise((resolve, reject) => {
  setTimeout(() => {
    https.get(url, (res) => {
      let str = '';
      res.on('data', (d) => {
        str += d;
      });
      res.on('error', (e) => {
        reject(Error(`error from promise reject:\n${e}`));
      });
      res.on('end', () => {
        if (res.statusCode !== 200) {
          reject(Error(`error from promise reject:\n${res.statusCode}`));
        }
        resolve(JSON.parse(str));
      });
    }).on('error', (e) => {
      reject(Error(`error from promise reject:\n${e}`));
    });
  }, t);
});

const runSeries = async() => {
  // series
  const data1 = await externalCall(goodUrl, 500);
  const data2 = await externalCall(goodUrl, 1000);
  return [data1, data2];
  //
  // series error is handled
  // const data1 = await externalCall(goodUrl);
  // const data2 = await externalCall(badDomain, 1000);
  // return [data1, data2];
  //
  // series error is handled
  // const data1 = await externalCall(badDomain);
  // const data2 = await externalCall(badDomain);
  // return [data1, data2];
};

const runParallel = async() => {
  // parallel
  // const data1 = externalCall(goodUrl, 500);
  // const data2 = externalCall(goodUrl, 1000);
  // return [await data1, await data2];
  //
  // parallel error is handled
  // const data1 = delayed(goodUrl);
  // const data2 = delayed(badDomain);
  // return [await data1, await data2];
  //
  // parallel error is not handled
  // const data1 = externalCall(badDomain);
  // const data2 = externalCall(badDomain);
  // return [await data1, await data2];
  //
  // better parallel
  const data1 = externalCall(goodUrl, 500);
  const data2 = externalCall(goodUrl, 1000);
  return Promise.all([data1, data2]);
  //
  // better parallel error is handled
  // const data1 = externalCall(badDomain);
  // const data2 = externalCall(badDomain);
  // return Promise.all([data1, data2]);
};

const api = async() => {
  // these two are equivalent
  // try {
  //   return await runParallel();
  // } catch (e) {
  //   return `error from try/catch: ${e}`;
  // }
  // return runSeries().catch(e => (`error from .catch():\n${e}`));
  return runParallel().catch(e => (`error from .catch():\n${e}`));
};

// let's pretend this is an api route called from somewhere
const route = () => {
  const now = new Date();
  api().then((data) => {
    console.log(data);
    console.log(`${new Date() - now}ms`);
  });
};

route();