On Jan 20, 2015, at 9:42 PM, Brendan Eich wrote:
> Mark S. Miller wrote:
>> Good, I understand now. I agree with all this. In ES6 the common cases have
>> to work right, and no guarantees compromised. Beyond the common cases,
>> extensibility we're confident in is great now. Otherwise, place restriction
>> where needed now (static and dynamic errors, inaccessible symbols) to make
>> the world safe for the extensibility directions we think we are likely to
>> want in the future.
>>
>> No exposed @toStringTag in ES6. Not because this extension point could grow
>> into an extensible branding mechanism (it can't), but because we're not yet
>> clear on how to prevent it from being mistaken for one.
>>
>> A fair summary?
>
> Fair. Allen?
It's a fair summary of where we were in the discussion last night. But after
having a night to stew on it, I've moved on and my current position is very
similar to Domenic's. I'll elaborate on that in a separate response.
There is no such thing as a symbol valued property key that is not exposed via
reflection. All properties keys are accessible via Object.getOwnPropertyKeys.
Here's all it takes to restore Symbol.toStringTag:
```js
function restoreSymbolToStringTag(taggedObject) {
//call this function with an object that is known to have a toStringTag
value. window might be a good candidate
let symbolKeys = Object.getOwnPrpertyKeys(taggedObject);
let desc = { }.toString.call(taggedObject);
let tagMatch = /\[object (.*)]'.exec(desc);
if (!tagMatch) return false;
let observedTag = tagMatch[1];
for (s of symbolKeys) {
try {
if (taggedObject[s]; === observedTag) {
//found it!
Synmbol.toStringTag = s;
return true;
}
} catch() {e) {};
}
return false; //not found
}
```
Allen
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