Understanding a simple piece of JS code - Functions -

Question

I am reading that Ninja Secrets of JS Book and seeing this part of example code:

    var ninja = {
      chirp: function signal(n) {                              //#1
        return n > 1 ? signal(n - 1) + "-chirp" : "chirp";
      }
    };

    var samurai = { chirp: ninja.chirp }; 

   ninja = {}; 

So I understand the first part: We have an object ninja and it has a method.

I understand the second part that ok now we are creating a new object called samurai and it has a property called chirp .

The part that confuses me is ninja.chirp part of it, what are we doing here? How is it working?

Answer 1

It takes the value of the chirp property of the ninja object (which is a function) and assigns it to the chirp property of the object being constructed.

Here is a simpler example (using a string instead of a function):

var foo, bar;
foo = { "an": "object" };
bar = { "an": foo.an }
alert(foo.an);
alert(bar.an);

Answer 2

I have seen this example so many times, and it is a horrible example. For starters, named function expressions are buggy in IE, but aside from that they are completely unnecessary as you can simply reference arguments.callee .

That aside, using a recursive function to repeat a string is just asking for trouble. The whole thing could be made so much more simply:

function signal(n) {
    return new Array(n+1).join("-chirp").substr(1);
}

Answer 3

In here, chirp its been copied to samurai . Than you can destroy the ninja object and still use the samurai.chirp method.