Globalization API discussion

Brendan Eich brendan at
Mon Nov 21 09:29:11 PST 2011

On Nov 21, 2011, at 8:49 AM, Allen Wirfs-Brock wrote:

> On Nov 20, 2011, at 8:30 PM, Brendan Eich wrote:
>> On Nov 20, 2011, at 1:18 PM, David Herman wrote:
>>>> I would not add more implicit magic to JS. E4X had junk like this in it, which only ever concealed bugs.
>>> I'm of two minds about this. In the abstract, I agree with Brendan; fail-soft conceals bugs. But in reality, our destructuring logic is incredible fail-soft. Hardly anything in destructuring is treated as an error. And the syntax really *wants* to match the common pattern. So I'm torn.
>> 1. Failing to write that means a destructuring parameter with default values within the pattern cannot be observed via arguments[i] as undefined (or null?). If missing, the undefined will be replaced by a fresh object. This isn't consistent with any other combination of destructuring parameters and parameter default values.
> Actually, I've specified parameter default value initialization such that the arguments object is an array of the actual argument values. It contains no default value substitutions. Even if function f({a,b}) is interpreted as function f({a,b}=undefined)  the value of arguments[0] for a call of the form f(undefined) would still be undefined.
> I'm not particularly in favor of treating undefined/null as { }, but I don't think the arguments object is particularly relevant to the issue.

If you had not preserved the actual undefined, I would argue differently. We all hate arguments but chipping away at consistency involving observations made using it has a bad smell.

What about points 2 and 3?


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