Ah! Good call. And, as expected, wrapping the first operand in parens makes the
problem go away.
REPL input is tricky to parse correctly in JS, kind of between statements and
expressions.
On Jan 27, 2012, at 16:56 , Bradley Meck wrote:
> Chrome and FF are treating the leading {} as an empty block statement.
>
> On Fri, Jan 27, 2012 at 9:47 AM, Axel Rauschmayer <[email protected]> wrote:
>> If I read ECMA-262 right then I would expect + to do the following if its
>> operands are either {} or []:
>>
>> - Convert each operand to a primitive via ToPrimitive()
>> - To do so, first try valueOf() (which returns an object which is thus
>> discarded), then toString()
>>
>> Finally, as at least one operand is a string, perform string concatenation.
>>
>> Hence not all of the following results in Firefox look OK to me:
>>
>> [16:33:50.214] [] + []
>> [16:33:50.217] "" // OK
>> --
>> [16:33:56.098] {} + {}
>> [16:33:56.099] NaN // Not OK
>> --
>> [16:34:02.455] {} + []
>> [16:34:02.456] 0 // Not OK
>> --
>> [16:35:38.002] [] + {}
>> [16:35:38.004] "[object Object]" // OK
>>
>> Node.js is better:
>>
>> $ {} + {}
>> '[object Object][object Object]'
>> $ {} + []
>> '[object Object]'
>>
>> Oddly, Chrome returns the same results as Firefox (different version of V8?)
--
Dr. Axel Rauschmayer
[email protected]
home: rauschma.de
twitter: twitter.com/rauschma
blog: 2ality.com
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