JavaScript Proxy object name does not match name of wrapped object
Categories
(Core :: JavaScript Engine, defect)
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People
(Reporter: alexander-mozilla, Unassigned)
References
Details
User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Steps to reproduce:
Open a JS console and compare the output of these two snippets:
Object.prototype.toString.call(window)
Object.prototype.toString.call(new Proxy(window, {}))
Actual results:
The first snippet produces the string "[object Window]", the second snippet produces the string "[object Object]".
Expected results:
They both should return "[object Window]" as an JS proxy should be maximally transparent to script using it.
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Comment 1•5 years ago
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@ntninja, if you're interested, follow bug 1277799.
The standard for Object.prototype.toString is awkwardly worded, but it boils down to:
- Try getting the property
obj[Symbol.toStringTag](step 15). If that is defined, use it. - Otherwise, use the builtinTag computed in steps 4-14. For Window objects, this is
"Object".
Note that the standard actually requires proxies to be treated non-transparently in steps 4-14. (Proxy policy is delicate business...)
However, the good news is that obj[Symbol.toStringTag] should be defined on Window and other DOM objects, according to the WebIDL standard. We just aren't doing that yet.
Description
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