Array#filter without callback function

Andrea Giammarchi andrea.giammarchi at
Mon Nov 12 13:29:05 PST 2012

if it's about iterating you have forEach which does not iterate over non
assigned indexes ... this looks like you want a new feature with an ES5
method as filter is so that you can use an ES3 for loop after ...

I mean, you have forEach, map, etc to iterate valid indexes, why would you
need that?

On Mon, Nov 12, 2012 at 1:24 PM, Asen Bozhilov <asen.bozhilov at>wrote:

> Hi,
> Array.prototype.filter could be used to convert sparse to dense array, e.g.
> [1,,,,,2,,,,,3].filter(Boolean.bind(null, true)); //[1, 2, 3]
> Would be pretty straightforward if built-in filter could be called without
> callback function and returns a dense array.
> I guess the engines will optimize that and library authors could
> gracefully iterate over index properties of arrays without checking for
> existance.
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> es-discuss at
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