Why isn't `toString` equivalent to `window.toString`?

Question

I'd believed that all global variables were accessible from the global object. So if I can access x (and x isn't bound locally), then window.x is the same value.

However, in a webpage (on JSFiddle):

window === this // true in Chrome and Firefox
toString === window.toString // true in Chrome and Firefox

But in the console:

window === this // true in Chrome console and Firebug, false in Firefox web console
toString === window.toString // false in Chrome, Firebug and Firefox web console

Why is this? Why is window the global object in Chrome's console but toString not bound to window.toString? What is toString bound to in Firefox's console? What other global values are different in the console?

Answer 1

I cannot reproduce your claim in Firefox. They're both returning [xpconnect wrapped native prototype].

To help clear this up: everything available globally IS available via the global object. However, there could be properties available through the global object that are not necessarily available globally. This is due to the prototypal inheritance pattern in Javascript and the lack of specification on how this situation should be handled.

So, should an interpreter attempt to resolve global lookups via prototypal inheritance down the global object chain? Does the global object inherit from anything else? I think the various Javascript interpreters are inconsistent here, but someone more familiar with ECMAScript specifications could weigh in.

Answer 2

perhaps this is related to this question? It's all related to the context, I believe

toString.call("foo") == this.toString.call("foo")

but

tostring.call("foot") != window.toString.call("foo") when this != window

Answer 3

toString is not a global variable. It's a method shared by almost all objects, including the window object.

An actual global variable would always be available on the window object.