ES3.1 questions and issues

Brendan Eich brendan at
Wed Mar 18 21:21:53 PDT 2009

On Mar 18, 2009, at 11:58 AM, Tobie Langel wrote:

> On Mar 18, 2009, at 17:20 , Allen Wirfs-Brock wrote:
>> Would it be useful if there was a way to determine whether nor not  
>> a function was "built-in"?
> That would be useful outside of the security concerns expressed by  
> Mark. I'm thinking about performance and robustness concerns in JS  
> libraries, for example.

Can you give an example?

We're self-hosting native methods that are called built-in by the spec  
in TraceMonkey, and I know V8 original self-hosted some Array and  
String methods. With the right isolation to avoid violating the spec,  
this is a good thing and it should not be prohibited.

Self-hosting built-ins also should not be the subject of second- 
guessing versionitis in JS libraries. Shades of coding C idioms for  
the microarchitecture of certain revisions of the x86!


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