If I read ES-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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