Is ES5 Strict a fully statically scoped language?

François REMY fremycompany_pub at yahoo.fr
Wed Oct 3 10:05:35 PDT 2012


I think that what he meant is that we know for sure in which scope we can find the property/variable. That the propery exists or not in the that scope is another issue.

So, in the code “function getOoops(t) { t(); return function() { return ooops; } }” we know statically that the scope where the “ooops” variable is defined is the global scope. At runtime, we just need to do “globalScope.get(‘oops’)" to retreive the value (or throw). In non-strict ES, the “t” function may be eval, and eval could add a “oops” variable in the parent function getOoops. So, we don’t know at compilation if “ooops” belong the the global scope of from the function’s scope (we can only find that out at runtime).



From: Šime Vidas 
Sent: Wednesday, October 03, 2012 6:41 PM
To: es-discuss at mozilla.org 
Subject: Is ES5 Strict a fully statically scoped language?
In the talk "Changes to JavaScript, Part 1: EcmaScript 5", Mark Miller states that ES5 Default contains four static scope violations (direct link: http://www.youtube.com/watch?v=Kq4FpMe6cRs&t=42m53s). He also states that ES5 Strict corrects these violations, making ES5 Strict is a statically scoped language. I don't understand how that can be true, since it is possible to dynamically add bindings to the global environment by creating new global properties (during code evaluation). Isn't this a static scope violation, too?

-- Šime Vidas



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