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

First, it has to be true to return, so if you are testing for truthfulness then it makes no difference

Second, it lets you do assignments along the lines of:

function bar(foo) {
    foo = foo || "default value";