JavaScript error handling with better `dx`

JavaScript expects you to handle errors with try...catch, but the syntax is somewhat inconvenient:

1. You have to declare result variables separately from your function calls.

const userInput = 'fail'

let json
try {
  json = JSON.parse(userInput)
} catch (err) {
  console.error(err.stack)
}

// Do something with `json`...

Since we declare json separately, we can't declare json as a const binding.

2. try...catch promotes catch-all error handling.

try {
  // A bunch of stuff happens...
  // ...
  // ...
} catch (err) {
  console.log('welp')
  console.error(err.stack)
}

You might want to handle errors in a more fine-grained way. But then you run into the verbosity of problem 1.

Enter dx

dx is a micro utility (it's just a few lines) that addresses the two pain points above.

import { dx } from '@nucleartide/dx'

const [res, err] = dx(JSON.parse)('invalid json')
if (err) {
  console.error(err.stack)
}

It allows you to place your declaration and function call on the same line. And it promotes a granular, per-function error handling style.

It also works with async functions:

import { dx } from '@nucleartide/dx'

function asyncHello(name) {
  return Promise.reject(`hello ${name}`)
}

;(async () => {
  const [res, err] = await dx(asyncHello)('jesse')
  if (err) {
    console.error(err.stack)
  }
})

Convinced?

Try it out and lemme know what you think! Also feel free to check out the source.

npm install @nucleartide/dx

Comments

[JavaScript Joel]

This is kind of like a poor man's Either!

[Darkø Tasevski]

What is this abomination:

;(async () => {

😱

[JavaScript Joel]

You cannot use async/await in the global scope. By wrapping your code in an async function, this trick will let you use await.

[Darkø Tasevski]

Are you sure about that? I know that you can't use await without async but if I remember correctly I've used async function in top-level scope a few times 🤔

Anyway, I was thinking about that semicolon at the beginning which purpose is to guard against AST, confusing and ugly syntax IMO.

[JavaScript Joel]

Are you sure about that?

You can test by pasting an await command into the browser console.

Anyway, I was thinking about that semicolon at the beginning

Ahh ya. It's just a guard.

[JavaScript Joel]

Where does the dx name come from? What does it mean?

[Jason Tu]

It could mean a lot of things? Developer Experience, De-Exception, Derivative, Ducks, etc.

I like the first 2 definitions best. Besides that, it's just short and convenient to type.

[Jason Tu]

You could always copy the module into your project! npm is just there as a convenience.

[Yoandy Rodriguez Martinez]

You Javascript people need Monads, or some decent metaprogramming, or macros, whatever make you stop creating libraries from every single useful snippet of code out there

[seyed mojtaba marashi]

good idea