Le 30/03/2012 07:17, Peter Michaux a écrit :
I've worked on a generic Set polyfill. It is quite a simple task to
build one but determining if an object is in the set is O(n) with the
following "has" method.
Set.prototype.has = function(element) {
for (var i = 0, ilen = this._elements.length; i< ilen; i++) {
if (element === this._elements[i]) {
return true;
}
}
return false;
};
It seems like a long shot but is there some trick that someone has
discovered that allows for a more efficient generic Set polyfill?
The issue here is that without native Set, the representations you have
of an object set requires to traverse it entirely the representation to
find something in it. This isn't true for sets of orderable things like
strings or numbers since orderable things could be ordered and found in
O(log(n)).
But opaque things like objects can't be ordered.
One idea would be that each Set puts a unique marker on each object it
contains as a non-enumerable property. Override
Object.getOwnPropertyNames, Object.preventExtensions|seal|freeze for
consistency. Much like the technique in
http://code.google.com/p/es-lab/source/browse/trunk/src/ses/WeakMap.js
Certainly not the best solution ever, but it seems like a step forward
assuming the costs of such a solution (in terms of performance and
security) is acceptable in your applications.
David
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