I'll bench it, about size this is 893 VS 914 ... not a big deal but scope
lookup is easier in my version.
Please consider this.enum break all minifiers since enum is a reserved word,
I had to do this["enum"] = {} at the end indeed.
Look if you find some hint here
(function (Object, exports) {
/**
* A simple enum implementation for JavaScript
* @link http://www.2ality.com/2011/10/enums.html
* @author @rauschma
* @revision @WebReflection
* @note enum is reserved word. Use var enm = this.enum or var
enm = require("enum");
*/
var // common shortcut
EnumPrototype = Enum.prototype,
defineProperty = Object.defineProperty,
forEach = [].forEach,
freeze = Object.freeze,
getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor,
getOwnPropertyNames = Object.getOwnPropertyNames,
keys = Object.keys
;
// module constructors
function Enum(obj) {
if (arguments.length == 1 && obj != null && typeof obj == "object")
{
forEach.call(keys(obj),
assignSymbolProperties,
{s: this, t: obj}
);
} else {
forEach.call(arguments, assignSymbol, this);
}
freeze(this);
}
function Symbol(name, props) {
this.name = name;
props && copyOwnTo(props, this);
freeze(this);
}
// helpers
function assignSymbol(name) {
this[name] = new Symbol(name);
}
function assignSymbolProperties(name) {
this.s[name] = new Symbol(name, this.t[name]);
}
function copyOwnTo(source, target) {
var names = getOwnPropertyNames(source);
names && forEach.call(names,
copyEachProperty,
{s: source, t: target}
);
return target;
}
function copyEachProperty(propName) {
defineProperty(
this.t,
propName,
getOwnPropertyDescriptor(
this.s,
propName
)
);
}
function mapSymbolValue(key) {
return this[key];
}
// secure Symbol prototype
freeze(
Symbol.prototype = Object.create(null, {
constructor: {
value: Symbol
},
toString: {
value: function toString() {
return "|"+this.name+"|";
}
}
})
);
// extend Enum prototype
defineProperty(EnumPrototype, "contains", {
enumerable: true,
value: function contains(sym) {
return sym instanceof Symbol ?
this[sym.name] === sym :
false
;
}
});
defineProperty(EnumPrototype, "symbols", {
enumerable: true,
value: function symbols() {
return keys(this).map(mapSymbolValue, this);
}
});
// exports
exports.Enum = Enum;
exports.Symbol = Symbol;
}(Object, typeof exports == "undefined" ? this["enum"] = {} : exports));
Best Regards,
Andrea Giammarchi
On Mon, Oct 24, 2011 at 11:53 PM, Axel Rauschmayer <[email protected]> wrote:
> If you don't want Object.prototype (why ?)
> do you want an enumerable, configurable, writable constructor ?
>
>
> I don’t care much either way. The main point for me is that symbol
> instances are immutable. If all of the instance’s prototype are also
> immutable, the instance itself is "more immutable". Again, I don’t have
> strong feelings for that.
>
> Why not just this ?
> exports.Symbol.prototype = Object.create(null, {constructor: {value:
> exports.Symbol}});
>
>
> I don’t see much difference with my solution, either regarding conciseness
> or regarding performance.
>
> Also why so many runtime closures and "var that = this" ?
>
>
> Runtime closures:
> - Does performance really matter here? I find my solution easier to read.
> - Note that binding "this" via forEach() and map() also has performance
> implications.
>
> that = this:
> - Your point is that forEach() and map() have a second parameter that
> allows you to hand in a value for "this", right?
> => I have yet to find a clear argument in favor or against using that =
> this here. Both solutions have performance implications, both solutions add
> an extra line. that = this has two extra tokens, but adding a second
> argument looks awkward.
>
> I would also drop all these anonymous functions using the closure with
> declarations for Symbol and Enum and export once at the end rather than
> reference the exports object each time.
>
>
> Yes, good idea, it’ll make things easier to read.
>
> --
> Dr. Axel Rauschmayer
> [email protected]
>
> home: rauschma.de
> twitter: twitter.com/rauschma
> blog: 2ality.com
>
>
>
>
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