Why result of ({} + []) not equal to ([] + {})

Asked Nov 19 '15 at 10:29

Active Nov 19 '15 at 10:38

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Javascript addition operation is easy to understand if there are only string and numbers or booleans.

But things getting harder with objects and arrays.

I looked into spec ECMA Script 3, 1999 11.6.1 and into Douglas Crockford Enciclopedia but both provided algorithms do not explain why:

[] + {}  // "[object Object]"
{} + []  // 0
{} + 0   // 0
0 + {}   // "0[object Object]"

{} + {}  // NaN, but not either 0 or "[object Object][object Object]"

Is anyone can explain this?

asked Nov 19 '15 at 10:29

nahab

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When you add Apples to Oranges, you get fruit Salad. And two Salads are never equal :) – Ranjith Ramachandra Nov 19 '15 at 10:33
Aside: https://www.destroyallsoftware.com/talks/wat – Andy Nov 19 '15 at 10:34
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According with [this](http://stackoverflow.com/a/11930789/4224126) answer you have a full explanation [here](http://www.2ality.com/2012/01/object-plus-object.html) – Adrian Menendez Nov 19 '15 at 10:37
Adrian Menendez thanks very much, I saw your answer, sorry for delay, I'm trying figured this out – nahab Nov 19 '15 at 10:39
You're welcome nahab, there is a good explanation on the Axel Rauschmayer post. – Adrian Menendez Nov 20 '15 at 12:12

Why result of ({} + []) not equal to ([] + {})

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