"Harmony is a super-set of ES5 strict"

Allen Wirfs-Brock allen at wirfs-brock.com
Fri Feb 25 15:17:32 PST 2011


On Feb 25, 2011, at 1:12 PM, Boris Zbarsky wrote:

> On 2/25/11 4:08 PM, David Bruant wrote:
>> I would tend to be more in favor of disallowing Harmony features in
>> non-strict code (without explicit "use strict" directive) to avoid
>> surprises (I'm nuancing below).
> 
> I was under the impression that Harmony features would only be allowed for scripts that opt in to them (via the type or language of the <script> tag or whatnot).  Does that alleviate this concern?
> 
> -Boris

The other subtlety is that this only applies only to the actual language features not to the behavior of objects. Any new property added to the existing built-in objects will most likely be visible to non-harmony code  and function and objects defined using harmony features (including Proxy) can be passed to and accessed by non-harmony code.  This is comparable to what happens in ES5 where non-strict code may call a strict mode function.

Allen



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