> Hi Kevin, thanks for pulling this code example out of the gist and posting
> separately. Looking at it only in context before, for some reason I hadn't
> realized how beautiful this is. To support this pattern, your makePrivate()
> could be defined either in terms of either private symbols or weakmaps,
> right?
>
Sure - but note that the implementation in the gist doesn't use either, per
se. It uses a new base-level API which provides the ability to get or set
private data for any (object, symbol) pair. Advantages of this approach
are:
- No need for for special case "private" object slots.
- Only one kind of Symbol.
- We can leave WeakMap as a strictly ephemeron data structure, like Allen
wants. No GC hint required.
I find this to be an intriguing "middle way". Here is the implementation
in full:
function makePrivate() {
// Create a symbol that names the private data
var symbol = new Symbol();
// Create a function for accessing the private data on some object
var priv = (obj, ...args) => {
if (args.length === 0) return Object.getPrivate(obj, symbol);
else return Object.setPrivate(obj, symbol, args[0]);
};
// Return the symbol so that we can share it...
priv.symbol = symbol;
return priv;
}
{ Kevin }
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