By doing a proper comparison:
x === y && y === z
// due to transitivity, if the above expression is true, x === z must be true as well
x==y==z is actually evaluated as
(x == y) == z
i.e. you are either comparing true == z or false == z which I think is not what you want. In addition, it does type conversion. To give you an extreme example:
[1,2,4] == 42 == "\n" // true
The problem is that when x==y and z==1, x==y==z will return true.
Yes, because x == y will be true, so you compare true == 1. true will be converted to the number 1 and 1 == 1 is true.
