name property for built-in functions??

David-Sarah Hopwood david.hopwood at
Sat Mar 7 07:11:12 PST 2009

Brendan Eich wrote:
> The utility of mutable name for anonymous functions is not at issue if
> we do not define name at all on such functions -- this is the proposal
> Allen and I were converging on. You can set name on such anonymous,
> expressed functions to whatever value you like, delete it, shadow it via
> .prototype/construction, etc.

I think that's a good solution; it meets the Objective-J use case without
introducing the mutability issue raised by MarkM.

> The only issue remaining in this anonymous function case is whether
> toString picks up the assigned name. For anonymous functions only, this
> could be done without breaking the isolation property that allowing
> mutation of the name initialized from the declared name of a
> non-anonymous function would break. In fact it would seem independent:
> anonymous function referenced by variable f:
>   * name can be set;
>   * if set to a value converting to the string "g", then f.toString()
> returns "function g(...) {...}" (modulo whitespace).

If name is set to a value that is not an Identifier, then the resulting
string might not be a syntactically correct FunctionExpression or

Of course a possible response is "Don't do that". Since the code that
is setting the name could do other things that would achieve the same
effect (for example, setting 'toString'), a "Don't do that" answer may
be adequate in this case. The function object can be sealed to prevent
all such mutations.

David-Sarah Hopwood ⚥

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