(Isn't that bananas, by the way?)
On Thu, Sep 17, 2015 at 5:26 PM, Shu-yu Guo <s...@mozilla.com> wrote:
> On Thu, Sep 17, 2015 at 5:18 PM, Neil <n...@parkwaycc.co.uk> wrote:
>
>> Shu-yu Guo wrote:
>>
>> 4. The global lexical scope is extensible. This means dynamic scope
>>> (lol!):
>>>
>>> <script>
>>> function f() { dump(x); }
>>> f(); // prints undefined
>>> </script>
>>>
>>> <script>
>>> let x = 42;
>>> f(); // prints 42
>>> </script>
>>>
>>> Would you mind clarifying what this is supposed to demonstrate? It looks
>> to me that this is demonstrating TDZ semantics, and under ES6 the first
>> call to f() will throw.
>>
>
> The first call to f() does not throw. These are two separate <script>
> tags, and during the execution of the first <script> tag, there is no
> global lexical binding named 'x', so no TDZ semantics are triggered.
> Instead, undefined is printed because there is no binding named 'x' and
> presumably the 'x' property on the global object is undefined.
>
> When we execute the second <script> tag, we now have made a global lexical
> binding named 'x'. When we call f() again, it will print the value of that
> binding.
>
> To contrast, the following two scripts would throw due to TDZ:
>
> <script>
> function f() { dump(x); }
> f(); // doesn't throw, prints undefined
> </script>
>
> <script>
> f(); // throws due to TDZ
> let x;
> </script>
>
>
> The second call to f() throws because during the second script's
> execution, there is an uninitialized global lexical binding 'x'.
>
>
>> --
>> Warning: May contain traces of nuts.
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>
>
>
> --
> shu
>
--
shu
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