What object are Javascript global variables stored in?

Question

Are global variables stored in specific object? For instance:

var test="stuff";
console.log(window.test);
console.log(document.test);
console.log(this.test);

All three of these tests result in undefined, so is there an object that holds these variables?

I feel as though this is something stupid that I should already know, but I can't even seem to find the answer online.

Answer 1

Here is a late but technical answer.

You ask

Are global variables stored in specific object?

The answer is yes; they are stored in something called, officially, the global object. This object is described in Section 15.1 of the official ECMAScript 5 Specification.

The global object is not required to have a name; but you can refer to its properties, such as String, isNaN, and Date simply by using their name. Your JavaScript host environment will place other properties in the global object besides the ones required by the ECMAScript specification, such as alert or console. In a browser, I can write the script

alert("Hello world");

because alert is a property of the global object.

Note that there does not have to be a way to access this global object at all, believe it or not. The cool thing, however, is that many host environments will put a property in the global object whose value is a reference to the global object itself. In most web browsers, this property is called window. So we can write:

alert("Hello");
window.alert("Hello");
window.window.alert("Hello");
window.window.window.window.window.alert("Hello");

and you can also say:

var x = 5;
alert(this.x);

and get 5 alerted.