Why does Chrome & FireFox console print 'undefined'?

Question

Take this simple Test object and paste it into the console. You'll see that it says undefined. The object is working because it also prints 123, but what is the undefined about?

Test:

var Test = new (function(){
    return {
        get testing(){
            return "123";
        }
    }
});

console.log(Test.testing);

Console Output:

123
undefined

Answer 1

That is the return value of console.log.

Try

console.log(1);

which gives

1
undefined

However, if you type just

Test.testing

that gives only

"123"