Null-coalescing assignment operator

[Xstoudi]

I open this issue to talk about nullish-coalescing assignment operator (??=) because I think it's maybe related to the nullish-coalescing operator. I was suprised to not see it in this current proposal because it could be really useful (as useful as a syntaxic sugar can be, at least).

The following example make use of proposal-class-fields. Something like that:

class Foo {
    #bar;
    get Bar() {
        this.#bar = this.#bar ? this.#bar : new Runner();
        return this.#bar;
    }
}

or

```js
class Foo {
    #bar;
    get Bar() {
        this.#bar =  this.#bar ?? new Runner();
        return this.#bar;
    }
}

would become

class Foo {
    #bar;
    get Bar() {
      return this.#bar ??= new Runner();
    }
}

As prior art:

• C# : https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/null-coalescing-operator
• PHP : https://wiki.php.net/rfc/null_coalesce_equal_operator

What do you think about it?

[jridgewell]

See https://github.com/tc39/proposal-logical-assignment (last discussed in 2018-03 meeting). The consensus was that the proposal could not advance until ?? landed (we didn't want to add ||= without ??= at the same time).

We'll be able to discuss it again soon! 😃

[Xstoudi]

What a fast answer! I'm happy to read that, I'll star the repo to participate when the time comes.