> What alternative do you want?
>
> 1. Parameter default value before default-free parameter means call without
> arity match throws?
>
> 2. What Oliver may have feared in switching to named parameters: actual
> argument list shorter than formal list with default on left causes parameter
> binding to skip defaults? This is not coherent:
>
> function foo(x, y = a, z = y) {...}
>
> foo() // x=undefined, y=a, z=a
> foo(1) // x=1, y=a, z=a
> foo(1, 2) // x=1, y=a, z=2???
> foo(1, 2, 3) // x=1, y=2, z=3
>
> 3. What ES6 draft says.
The only thing I can see are two, mutually exclusive, modes:
1. Trailing optional positional parameters.
2. Leading optional positional parameters.
There are a few cases, were #2 would be useful. I don’t see other alternatives
that make sense. But that may be due to a lack of understand why one would want
to have default values in an order that is neither #1 nor #2.
Axel
--
Dr. Axel Rauschmayer
a...@rauschma.de
home: rauschma.de
twitter: twitter.com/rauschma
blog: 2ality.com
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