While a |foo| variable is visible through a call to |window.foo|, a |bar| const is always undefined through a call to |window.bar|. This was not the case before the changes introduced for let and const for ES6. Since I see nothing in ES6 that makes this mandatory (this is more a conformance with Chrome), I'm filing this bug. Codepen: http://codepen.io/anon/pen/RaZyMX FWIW, a feature of BlueGriffon was completely horked because of that...
The standard does require this. Otherwise we would never have implemented it, as it horked a ton of stuff for us throughout Firefox. Ask :shu about it sometime. I don't blame you for being unable to find this in the standard, which is practically impenetrable even for people who have lived in there for years. But here's the summary: * ECMA-262 15.1.11 GlobalDeclarationInstantiation <https://tc39.github.io/ecma262/#sec-globaldeclarationinstantiation> specifies how global variable are set up; this happens just before the code of a script starts to run. Step 16.b.i.1 creates `const` bindings by calling CreateImmutableBinding. Step 18.a creates `var` bindings by calling CreateGlobalVarBinding. * CreateGlobalVarBinding is defined in 220.127.116.11.17 <https://tc39.github.io/ecma262/#sec-createglobalvarbinding>. It creates a binding in envRec.[[ObjectRecord]] which entails defining a property on the global object. * CreateImmutableBinding for global environments is defined in 18.104.22.168.3 <https://tc39.github.io/ecma262/#sec-global-environment-records-createimmutablebinding-n-s>. It creates an entry in envRec.[[DeclarativeRecord]], which is the "global lexical scope". No objects are touched. I don't like the global lexical scope. Never did. It's awful. But, we follow the spec. Not sure if this will help, but there is also <https://hacks.mozilla.org/2015/07/es6-in-depth-let-and-const/> which talks about all this nonsense in less technical terms.
Status: NEW → RESOLVED
Closed: 3 years ago
Resolution: --- → INVALID
Jason, thanks for the detailed info, and sorry then for the spam. If I completely understand that following the spec is needed, please allow me to say that part of the spec is stupid and impossible to understand from a JS author's perspective who's not used to dive into Ecma specs. I find this totally ridiculous and would definitely and strongly support Mozilla if it brings the issue to Ecma (or bring it again, more probably). Anyway, thanks again.
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