# Positional binding after rest binding?
**URL:** https://es.discourse.group/t/positional-binding-after-rest-binding/2380
**Category:** 💡 Ideas
**Created:** [June 10, 2025, 5:32am UTC](https://es.discourse.group/t/positional-binding-after-rest-binding/2380 "2025-06-10T05:32:32Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@claudiameadows](https://es.discourse.group/u/claudiameadows)
#### Post date: [June 10, 2025, 5:32am UTC](https://es.discourse.group/t/positional-binding-after-rest-binding/2380/1 "2025-06-10T05:32:32Z")
Related: [rest end only but not rest start only?](https://es.discourse.group/t/rest-end-only-but-not-rest-start-only/1788)
_I also recall this being discussed on the old es-discuss mailing list, but dredging through that isn't something I feel like doing._
I'd like to see stuff like `(a, ...bs, c) => ...` be possible. To name a few examples of use case and precedent:
- Node's callback idiom the whole time has been `f(...args, callback)`, and any function forwarding all but the callback needs to have such a prototype.
- [GitHub - scijs/ndarray: 📈 Multidimensional arrays for JavaScript](https://github.com/scijs/ndarray) has an `ndarray.set(...indices, value)`.
- CoffeeScript supported this since before ES6. ES6 got its very rest parameter idea in part from it, so it's pretty strong precedent. I think Babel and/or Traceur also once supported it as an extension way back then.
There's of course a lot more, and I could probably spend hours just finding and adding precedent here.
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### Author:  [@claudiameadows](https://es.discourse.group/u/claudiameadows)
#### Post date: [June 10, 2025, 5:35am UTC](https://es.discourse.group/t/positional-binding-after-rest-binding/2380/2 "2025-06-10T05:35:45Z")
I also found this, and I'm not sure why it didn't show up in my search results: [Inverse Rest Operator](https://es.discourse.group/t/inverse-rest-operator/1973)
This is a near dupe of that, just a little more detailed.
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### Author:  [@michael](https://es.discourse.group/u/michael)
#### Post date: [June 25, 2025, 5:41pm UTC](https://es.discourse.group/t/positional-binding-after-rest-binding/2380/3 "2025-06-25T17:41:04Z")
I think this would be great. If I recall correctly from when rest parameters were added, the restriction was not due to any objections or challenges, it was just to make a small first step.
Note that we'll have to make sure there's an easy way for the average developer to understand the interactions between non-final rest parameters and default parameters. Banning their mixing is probably the easiest way to go about it.
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### Author:  [@tabatkins](https://es.discourse.group/u/tabatkins)
#### Post date: [June 25, 2025, 7:55pm UTC](https://es.discourse.group/t/positional-binding-after-rest-binding/2380/4 "2025-06-25T19:55:46Z")
> If I recall correctly from when rest parameters were added, the restriction was not due to any objections or challenges, it was just to make a small first step.
Yeah, avoiding `[...foo, bar]` let us skip answering some hard questions and just get the 90% use-case solved. No matter what you define, people can expect different behavior for `let [a, ...b, c] = [1]`/etc, so it's a much tougher judgement call.
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### Author:  [@michael](https://es.discourse.group/u/michael)
#### Post date: [June 25, 2025, 8:33pm UTC](https://es.discourse.group/t/positional-binding-after-rest-binding/2380/5 "2025-06-25T20:33:40Z")
I think we can learn a lot from the choices and experience of CoffeeScript there. IMO this proposal is very much in the realm of feasible.