On Jan 3, 2012, at 15:46 , Greg Smith wrote:
> What is the use case for .repeat? Trying to imagine some code where I'd need
> it so I can get a feel for how it should work.
So beauty alone does not count? ;-)
It’s true – there are not a lot of use cases for Array.repeat().
But I keep thinking that there should be a way to create an array of a given
length *with* content in it. Rationale: such an array is nice to have as a
starting point for a transformation via Array.prototype.map() or an array
comprehension [1]. How about the following?
Array.range = function (start, end) {
if (arguments.length < 1 || arguments.length > 2) {
throw new TypeError("Need one or two arguments");
}
if (arguments.length === 1) {
end = start;
start = 0;
}
var result = [];
for(var i=start; i < end; i++) {
result.push(i);
}
return result;
}
Interaction:
> Array.range(4)
[ 0, 1, 2, 3 ]
> Array.range(4).map(function () { return "*" })
[ '*', '*', '*', '*' ]
I’m not yet sure how many use cases there are (suggestions welcome), but it
does fill a hole (IIRC, Python has something similar).
TODO: This method probably makes more sense as an iterator (e.g. implemented
via a generator). Then one could even omit the upper limit and produce an
unlimited sequence.
[1] http://wiki.ecmascript.org/doku.php?id=harmony:array_comprehensions
--
Dr. Axel Rauschmayer
a...@rauschma.de
home: rauschma.de
twitter: twitter.com/rauschma
blog: 2ality.com
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