On Apr 16, 2010, at 12:51 PM, Erik Arvidsson wrote:
On Fri, Apr 16, 2010 at 08:43, Brendan Eich <bren...@mozilla.com>
wrote:
ES4 since Waldemar's 1998-era JS2 work was concerned with the
problem of versioning APIs implied by (1) greatly, and not just
adding properties: deleting and redefining too. ES4 proposed
namespaces (like Common Lisp packages, IIRC) as the solution. But
namespaces are out for Harmony.
My hope is that we can avoid versioning the object model and instead
simply extend certain objects that we effectively "reserve to the
implementation" (as ANSI and then ISO C does with certain global
names, e.g. __foo and _BAR). Indeed Ajax library developers now
generally avoid extending standard prototypes, and it's plausible
this best-practice could be extended to the built-in constructor
objects too.
These are considered best practices because it breaks in the
presence of other code outside your control. There is a reason why
Prototype.js is popular. It allows people to write code in a more
sane way, using methods that are bound to objects instead of global
functions. If we had something like ES4 namespaces without all the
issues (one can always dream) I'm sure that this best practice would
be reversed.
You're right -- I hear this from lots of developers. Ben Galbraith,
for example, says Prototype reduces keystrokes and he's right,
keystrokes aggregated over a long time do count. There is a
corresponding readability issue.
I was describing things as they are, not as they might be. But we do
not have a namespace solution.
However, ES5 *does* allow libraries to bind non-enumerable properties
of prototype objects. This is half of the solution, and if the
prototype in question is Object.prototype, or perhaps even then if the
name is obscure enough, a library might risk breaking object detection
on that name in the global object.
Another Harmony idea: http://wiki.ecmascript.org/doku.php?id=strawman:names
for unforgeable property names not equated to any string. These
cannot collide, and with sugar to let them be used with . (not only in
computed property accesses using []), we may have a complete solution
for injecting new "names" into standard prototypes without breaking
existing code.
/be
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