The proposal we accepted, written by Andreas at
http://wiki.ecmascript.org/doku.php?id=harmony:refutable_matching, seems
clear. Patterns are refutable without an extra ? annotation. Andreas is
using prefix-?, note well.
/be
Axel Rauschmayer wrote:
Are patterns in parameter declarations irrefutable? In other words,
given:
function foo({ opt1 }) { return opt1 }
What happens if we call foo()?
1. An exception is thrown
2. undefined is returned
I’d expect (2). If opt1 had a default value, I’d expect that value to
be returned.
What happens if we call foo({})?
1. An exception is thrown
2. undefined is returned
I’m asking, because I’ve seen the pattern
function foo({ opt1 = 3 } = {}) { return opt1 }
If explicitly marking something as irrefutable is necessary, I’d prefer:
function foo({ opt1 = 3 }?) { return opt1 }
It’s a bit of a shame that destructuring and parameter declarations
diverge, but I guess it can’t be helped.
Axel
--
Dr. Axel Rauschmayer
a...@rauschma.de <mailto:a...@rauschma.de>
home: rauschma.de <http://rauschma.de>
twitter: twitter.com/rauschma <http://twitter.com/rauschma>
blog: 2ality.com <http://2ality.com>
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