Question

I’m reading this post. It defines a simple array:

var myArray = [1, 2];
myArray.push(3);
myArray.reverse();
myArray.pop();
var length = myArray.length;

and then tries (and succeeds) in getting its prototype via Object.getPrototypeOf. However, when I tested this in Firebug and Chrome’s console, I get an empty array. Why?.

However, when I do the same for an object (in this case, the point object defined in the same post), I actually get its prototype.

Answer 1

Chrome’s Developer Tools displays Array.prototype as an array, because it suffices the two requirements for this behaviour:

• having a .length property
• having a .splice function

Array instances have these properties, so you see arrays as actual arrays which is helpful. The problem is that Array.prototype also is an array according to Chrome’s Developer Tools because of these rules (which it also is, but it’s not a very helpful visualisation because it shouldn’t have elements).

If you evaluate Object.getPrototypeOf(myArray) === Array.prototype, you’ll get true. It’s just Chrome’s Developer Tools that doesn’t display Array.prototype as you might expect.