Array destructuring

[sebdeckers]

Seems like this syntax triggers a false positive, or maybe my ES6 understanding is lacking.

Input

let [a, b = {}] = [1, 2]
a
b

Output

3:0: 'b' is not defined. (no-undef)

[Flet]

I dont think b = {} is valid.
Putting it into Firefox console yields:

let [a, b = {}] = [1, 2]
SyntaxError: missing variable name

But this works

let [a, b] = [1, 2]

[sebdeckers]

In Firefox, default values for destructuring assignments are not yet implemented: var { x = 3 } = {} and var [foo = "bar"] = []. See bug 932080 and also bug 1018628 for destructured default values in functions.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment

[feross]

Cool, thanks for debugging this.

[dcousens]

@feross so wait, is the conclusion that it is an eslint issue?

[sebdeckers]

@feross Why was this closed? 😕

Could be related to eslint/eslint#2405

[Flet]

Reopening :)
I think @CBas was just showing me that default assignment for destructing arguments is not in Firefox yet. :) Thanks for the info btw!

That eslint issue links to the real issue which is in escope estools/escope#33

[feross]

Ah, sorry I misunderstood what this issue was about. ;) Thanks for re-opening @Flet.

[feross]

This issue is fixed. Not sure which version it was fixed in, but there's no longer an error when linting:

let [a, b = {}] = [1, 2]
a
b

Nice!