Swiftly Optional

Optionals for JavaScript, inspired by Swift.

Installation

Install via npm:

npm i swiftly-optional

Import the module in Node:

const Optional = require('swiftly-optional')

Or in Babel:

import Optional from 'swiftly-optional';

Usage

First, wrap an object in a new Optional construction:

const myOptional = new Optional(objData)

Now, when accessing an object, you can add an underscore to object properties that may or may not exist, and JS won't throw errors:

myOptional.a_.b_.c_.d

In the example above, if any of the properties a, b, or c do not exist, then undefined will be returned.

Why do I need this?

Handling nested properties of an object in JavaScript is clumsy and verbose. Let's say we want to display a user's hometown as a string with a "city, country" format. A user object might look like this:

user = {
  name: 'Joe',
  profile: {
    location: {
      city: 'Boston',
      country: 'USA'
    } 
  }
}

Or it might be less complete and look like this:

user = {
  name: 'Joe',
  profile: null
}

Or it might have not been found at all, in which case user might simply be undefined. How do we handle these unknowns? Well, of course, in a perfect world, the structure of the object would be entirely consistent and we could always get away with this:

`${user.profile.location.city}, ${user.profile.location.country}`

But if we can't guarantee that, for whatever reason, then we need to check our values before we attempt to access them. What many devs intuitively want to do is:

const location = user.profile.location
if (location) { return `${location.city}, ${location.country}`}

But if user or user.profile are undefined or null, then we'll get an error. So then we can either check for truthiness at every level of nesting:

if (user && user.profile && user.profile.location) {
  const location = user.profile.location
  return `${location.city}, ${location.country}`
}

Or we can use a try/catch block:

let location = ''
try {
  location = user.profile.location
} catch (e) {}
return `${location.city}, ${location.country}`

There are many variations of those two basic approaches, and they do work. But they're not elegant. Swift's optionals provide a simple, clean way of accessing nested values without hitting errors. A Swift optional might look like this:

let location = user.profile?.location
if (location != nil) { return location!.city + ", " + location!.country }

That happens to be remarkably similar to the intuitive approach that most developers want to take in JS, but can't.

Enter Optionals.

Unfortunately, question marks aren't valid variable names, so we can't imitate Swift perfectly. But underscores are valid, and we can use them as a substitute. Here's the example above, with Swiftly Optionals, for JavaScript™️:

let user = new Optional(userData)
let location = user.profile_.location
if (location) { return `${location.city}, ${location.country}` }

Not too shabby. Here's a complete example:

const Optional = require('swiftly-optional')

const users = [
  {
    name: 'Joe',
    profile: {
      location: {
        city: 'Boston',
        country: 'USA'
      } 
    }
  }, {
    name: 'Joe',
    profile: null
  }, 
  undefined
]

users.forEach( user => {
  let location = Optional(user).profile_.location
  if (location) {
    console.log( `${location.city}, ${location.country}` )
  }
})