Why don't logical operators (&& and ||) always return a boolean result?

Question

Why do these logical operators return an object and not a boolean?

var _ = (obj.fn && obj.fn() ) || obj._ || ( obj._ = {} );

var _ = obj &&          


        

Answer 1

var _ = ((obj.fn && obj.fn() ) || obj._ || ( obj._ == {/* something */}))? true: false 

will return boolean.

UPDATE

Note that this is based on my testing. I am not to be fully relied upon.

It is an expression that does not assign true or false value. Rather it assigns the calculated value.

Let's have a look at this expression.

An example expression:

var a = 1 || 2;
// a = 1

// it's because a will take the value (which is not null) from left
var a = 0 || 2;
// so for this a=2; //its because the closest is 2 (which is not null)

var a = 0 || 2 || 1;    //here also a = 2;

Your expression:

var _ = (obj.fn && obj.fn() ) || obj._ || ( obj._ = {} );

// _ = closest of the expression which is not null
// in your case it must be (obj.fn && obj.fn())
// so you are gettig this

Another expression:

var a = 1 && 2;
// a = 2

var a = 1 && 2 && 3;
// a = 3 //for && operator it will take the fartest value
// as long as every expression is true

var a = 0 && 2 && 3;
// a = 0

Another expression:

var _ = obj && obj._;

// _ = obj._