Why is window not identical to window.self in Internet Explorer?

Question

There\'s a convoluted backstory involving how I came across this, but why is the self property not exactly equal to the window itself?

In Safari and Fir

Answer 1

Nice question. It does it with document and document.parentWindow too:

window == document; // true
window === document; // false

window == document.parentWindow; // true
window === document.parentWindow; // false

The big wtf for me though is:

window == document; // true
document == window; // false

You can swap out window with this in any of the above examples (and stay in the global context) with the same results. It makes the == operator even more suspect.

Why it behaves this way is so beyond me.