Why were namespaces removed from ECMAScript consideration?
- by Bob
Namespaces were once a consideration for ECMAScript (the old ECMAScript 4) but were taken out. As Brendan Eich says in this message:
One of the use-cases for namespaces in
ES4 was early binding (use namespace
intrinsic), both for performance and
for programmer comprehension -- no
chance of runtime name binding
disagreeing with any earlier
binding. But early binding in any
dynamic code loading scenario like
the web requires a prioritization or
reservation mechanism to avoid early
versus late binding conflicts.
Plus, as some JS implementors have
noted with concern, multiple open
namespaces impose runtime cost unless
an implementation works
significantly harder.
For these reasons, namespaces and
early binding (like packages before
them, this past April) must go.
But I'm not sure I understand all of that. What exactly is a prioritization or reservation mechanism and why would either of those be needed? Also, must early binding and namespaces go hand-in-hand? For some reason I can't wrap my head around the issues involved. Can anyone attempt a more fleshed out explanation?
Also, why would namespaces impose runtime costs? In my mind I can't help but see little difference in concept between a namespace and a function using closures. For instance, Yahoo and Google both have YAHOO and google objects that "act like" namespaces in that they contain all of their public and private variables, functions, and objects within a single access point. So why, then, would a namespace be so significantly different in implementation? Maybe I just have a misconception as to what a namespace is exactly.
