Discussion on: Clean up your code with these tips!

[Mihail Malo]

Out of curiosity, before reading the article I copied the initial example and tried my best on it myself.

This is what I ended up with:

const needsSecure = () => {
  const hostname =
    typeof window !== "undefined" &&
    window.location &&
    window.location.hostname
  if (!hostname) return true

  if (hostname === "localhost" || hostname === "127.0.0.1") return false

  return true
}

const secure = needsSecure()

export default new Cookie({ secure })

On one hand, I feel ridiculous I have a function that will only run once.
On the other, there are no let bindings in the file.

I did consider Array.prototype.includes() but elected not to use it for just two elements.

I don't think the RegEx has good readability, especially having had to escape the dots.

I also noticed that you used === for comparing to "undefined" but == for the domain.

Is there a reason you are using hasOwnProperty instead of just the truthiness of the objects? Is it more performant?
Myself, in the process of writing this, I went back and changed it, and was happily surprised that

// the expression
window.location.hasOwnProperty("hostname") &&
window.location.hostname
// collapsed to
window.location.hostname

[DeChamp]

So I loved that you took try at it. You did good!

Doing a function is typically a sure thing. It's never stupid to abstract out to a function. It's a great habit to practice. Even if it only gets used once, you are completely right about it helping to avoid having to do things such as declaring additional variables and also making the assignment highly clear const secure = needsSecure() vs const secure = !isLocal;.

Now far as this part, you can do 1 better.

const needsSecure = () => {
  const hostname =
    typeof window !== "undefined" &&
    window.location &&
    window.location.hostname
  if (!hostname) return true

  if (hostname === "localhost" || hostname === "127.0.0.1") return false

  return true
}

this instead, removing an additional if statement.

const needsSecure = () => {
  const hostname =
    typeof window !== "undefined" &&
    window.location &&
    window.location.hostname

  if (hostname && (hostname === "localhost" || hostname === "127.0.0.1")) return false

  return true
}

With the RexEx, that was more of an option to show others that you could bring in RegEx to do your checking. But you and others have pointed out, that my goal was to make the code more readable... so to a lot of people, it's hard to read so therefore it did not make the code "easier to read".

Far as strict comparison, vs non-strict. That is a bad habit I need to break. You caught me red-handed lol. Stick with using strict comparison, and only use non-strict as needed.

Now for the final part, hasOwnProperty is there for a good reason. I am wanting to specifically check for a Boolean answer, so hasOwnProperty will give me that. You can definitely do it your way and it'll work. When it's a single variable, that is how I do it.

When I'm digging down in to an object I prefer to be more intentional with it by using hasOwnProperty

[Mihail Malo]

So then, something like this?

typeof window !== "undefined" &&
  window.hasOwnProperty("location") &&
  window.location.hostname

I guess.

It's actually really unclear how to do such checks, you have to keep in mind what failures you actually expect to have.
On one hand, if you expect an object, truthiness gets rid of null, undefined, false (we'd be getting the false from the typeof equality, as well as hasOwnProperty) as well as less importantly 0, and "".

// OH NO
;({ location: undefined }.hasOwnProperty("location")) // true
;({ location: null }.hasOwnProperty("location")) // true
// Better I guess
!!({ location: undefined }).location // false

But on the other hand, if you expect a number, you will have weird failure on 0, which is very commonly a normal number. In which case you often check for undefined.

const fn1 = (num = 1) => num // How would we write this without default notation?
const fn2 = num => num || 1 // NO, YOU DIE!
const fn3 = num => (num === undefined ? 1 : num) // it's okay to not use typeof x === "undefined" in this context, it's a declared argument.

But it doesn't solve everything!

const window = { location: { hostname: { valueOf: () => "localhost" } } }
const hostname = typeof window !== "undefined" && window.location && window.location.hostname
""+hostname === "localhost" // The triple equals won't save you now, once string concatenation happened!

Maybe we should always use typeof :/
But what is your next action if hostname is an object? Pretending it wasn't set and defaulting to secure?

const needsSecure = () => {
  const hostname =
    typeof window === "object" &&
    typeof window.location === "object" &&
    typeof window.location.hostname === "string" &&
    window.location.hostname

  if ((hostname && hostname === "localhost") || hostname === "127.0.0.1")
    return false

  return true
}

Honestly, truthiness seems like the best bet to me, I just need to keep track of when it can be a 0 or "" or a literal significant false and it'll be okay.
I think I'll just keep using that.

> (undefined).potatoes
//TypeError: Cannot read property 'potatoes' of undefined
> (null).potatoes
//TypeError: Cannot read property 'potatoes' of null
> (true).potatoes
undefined // And it will never be anything truthy on a non-object, right? RIGHT?
> (true).valueOf
[Function: valueOf] // OH GOD DAMMIT!!