Discussion on: 😲🤯The most outstanding new feature in Javascript you need to know about: Optional Chaining

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Replies for: Why const personFirstName = person?.details?.name?.firstName ?? 'stranger' Rather than const personFirstName = person?.details?.name?.first...

Good question!
Example time!

const user = {
    auth: {
        isLoggedIn: false
    }
}

const isLoggedIn = user.auth?.isLoggedIn || true
// isLoggedIn would be true!

const isLoggedIn = user.auth?.isLoggedIn ?? true
// isLoggedIn would be false!

As you can see there is a difference in how they work.
The problem with || is that it will return the right value when the left value is falsy. The ?? just checks for null or undefined.

Joshua Sanger • Sep 16 '19

Could also consider converting to a true/false value with:

const isLoggedIn = !!(user.auth?.isLoggedIn)

Carlos Trapet • Sep 18 '19

@joshua I was literally going to say the same thing.
I fail to see the point/usefulness of the '??' operator

Michael "lampe" Lazarski • Sep 18 '19

There are always alternatives if you can also write

if(user.auth?.isLoggedIn === true){
    // user is logged in!
}

Nobody is forcing anybody to use the ?? operator but I think it just fits nicely together with the ?. and makes the intent clear if the developer knows how both of them work.