Parameter lists as arguments destructuring sugar

Brendan Eich brendan at mozilla.com
Sun Apr 10 09:32:25 PDT 2011


On Apr 9, 2011, at 10:08 PM, Sean Eagan wrote:

> function ({a, b}){}
> //or
> function ({a: b, c: d}){}

This has been implemented since at least Firefox 3 (also IINM supported in Rhino):

js> function f({a, b}){print(arguments[0], arguments.length, a, b)}
js> f({a:42, b:99})
[object Object] 1 42 99
js> function g({a:x, b:y}){print(arguments[0], arguments.length, x, y)} 
js> g({a:43, b:100})
[object Object] 1 43 100

It is part of the Harmonious Proposal.

The actual (positional) parameters reflect as arguments properties, while the formal (destructured-to) variables are local bindings equivalent to var declarations, initialized before the body of the function is evaluated.

/be


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