Question

Why would you use this syntax?

var myVar = myArray.length && myArray || myObject;

instead of

var myVar = myArray.length ? myArray : myObject;

Edit: I just had a thought that if in the case of the && || syntax both sides of the || evaluated to false, as you might expect if myObject was undefined or null, if false would be returned. But it isn’t, the objects value undefined or null is returned.

true  ||  true      //true
true  ||  false     //true
false ||  true      //true
false ||  false     //false

Edit2:

!!(myArray.length ? myArray : myObject);

This does however return false if myObject is undefined or null

Answer 1

x && y || z is different than x ? y : z even if it “works” in the case presented.

Consider when y evaluates to a false-value (in the post y can’t be a false-value when it is evaluated because it is dependent upon x and thus it “works” as expected).

Using ?: is the much better and more clear construct in this case. The only reason I can give for using the other syntax is “too much cleverness”.