Node: Error handling, async Vs. error-first.

node-async-error.js

const api = require('./node-error-api.js');

// Not an error-first callback
let callbackFunc = (data) => {
   console.log(`Something went right. Data: ${data}\n`);
};
  
try {
  api.naiveErrorProneAsyncFunction('problematic input', callbackFunc);
} catch(err) {
  console.log(`Something went wrong. ${err}\n`);
}

node-error-api.js

module.exports = {
  errorProneAsyncApi: (input, callback) => {
    console.log(`Running errorProneAsyncApi with input: ${input}...\n`)
    setTimeout(() => {
      let myErr;
      if (input === 'problematic input') {
        myErr = new Error('whoops')
        callback(myErr)
      } else {
        let responseData = `Received valid input "${input}"`
        callback(myErr, responseData)
      }
    }, 0)
  },
  
  naiveErrorProneAsyncFunction: (input, callback) => {
    console.log(`Running naiveErrorProneAsyncFunction with input: ${input}...\n`)
    setTimeout(() => {
      if (input === 'problematic input') {
        throw new Error('whoops')
      } else {
        let responseData = `Received valid input "${input}"`
        callback(responseData)
      }
    }, 0)
  }
  
}

node-error-first.js

const api = require('./node-error-api.js');

// An error-first callback
let errorFirstCallback = (err, data) => {
  if (err) {
    console.log(`Something went wrong. ${err}\n`);
  } else {
    console.log(`Something went right. Data: ${data}\n`);
  }
};

api.errorProneAsyncApi('problematic input', errorFirstCallback);