Here is the result from browser console (both firefox and chrome ) ,
false == {} works,but {} == false gives syntax error.
>> false == []
true
>> false == {}
false
>> 0 == false
true
>> false == []
true
>> false == {}
false
>> [] == false
true
>> {} == false
Uncaught SyntaxError: Unexpected token ==
In the former case, it's not clear to the parser that {} represents a value.
The following works:
var a = {};
a == false // false
Or alternatively you can use:
({}) == false // false
So this isn't anything specific to value comparison -- rather, it's the way the code is parsed.
Nice question!
If you run just {}, you see that it's not being parsed as an object at all - it gives undefined! Clearly, it's being parsed as a code block. Hence, {} == false is a syntax error, as there is nothing on the left side of the ==.
{}variableName is also not a syntax error for the same reason - it's an empty code block.
If you wrap it in parentheses, it is correctly parsed as an object literal, and works.
({}) == false
Even this works,
/{}/ == false; // false
