On Mar 17, 2008, at 3:08 PM, Mike Shaver wrote:
> On Mon, Mar 17, 2008 at 5:36 PM, Brendan Eich <[EMAIL PROTECTED]>
> wrote:
>> For backward compatibility with SpiderMonkey, one might like 2' to
>> make a getter that can be deleted.
>
> That pattern is used in Firefox now (and perhaps elsewhere) to do lazy
> initialization of expensive objects:
>
> this.__defineGetter__("Debug", function() {
> var d = loadModule("debug.js");
> delete this.Debug;
> this.Debug = d;
> return d;
> });
>
> We could adapt, obviously, dunno if it's widely used on the web.
With only SpiderMonkey supporting __defineGetter__, it's not widely
used. The canonical JS memoization pattern, presented nicely here:
http://osteele.com/archives/2006/04/javascript-memoization
changes (shadows or replaces) a function-valued property, requiring
callers to add pesky () to invoke the property explicitly. With
getters and setters, this noise-problem can be avoided and (beyond
noise reduction) old client code that wanted to get a property, not
call a method, can be made to call a memoizing wrapper without
requiring vast or infeasible (you don't own write access to the
client code) search and replace work.
So getters and setters plus memoization patterns do summon
__defineGetter__, in our experience.
/be
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