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

In the simplest terms:

The || operator returns the first truthy value, and if none are truthy, it returns the last value (which is a falsy value).

The && operator returns the first falsy value, and if none are falsy, it return the last value (which is a truthy value).

It's really that simple. Experiment in your console to see for yourself.

"" && "Dog"    // ""
"Cat" && "Dog" // "Dog"
"" || "Dog"    // "Dog"
"Cat" || "Dog" // "Cat"