[kmill]

Javascript is a lot saner than that. The result is "12". (I'm ok with automatic casting so long as it's an embedding. Every number has a reasonable string representation, but not vice versa. Wanting explicit casts like in Python is defensible, though.)

[SonOfLilit]

Huh, what do you know.

Still, this is unforgivable in my book:

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

[kmill]

For the first, I frequently (for my own projects) change the Array prototype to have

   Array.prototype.toString = function () {
      return '[' + this.join(', ') + ']';
   };

It would be convenient if Object.prototype.toString by default threw an exception, since the default breaks the embedding rule I described.

The second example is misleading, and it has nothing to do with the rules for addition: the {} at the beginning of the expression is parsed as a code block, played off the rules for what the value of a Javascript statement is. More realistically, we have

   ({}) + [] == "[object Object]"

but the original is, effectively,

   {
   }
   console.log(+[]);

[SonOfLilit]

I didn't realise about the second one. Thanks!

[skykooler]

Thanks, I never realized that the second one was parsed as a code block rather than an object!