document.defaultView === window circular reference?

Question

So I read that document.defaultView in JavaScript DOM points to the window object. Doesn't this become a circular reference and crash the document?

Since I'm new to JavaScript, DOM, and Black Magic, it stumps me that things like this are valid:

console.log(window.document.defaultView === window); //true
console.log(window.document.defaultView.document.defaultView === window); //true

Any thoughts?

Answer 1

正如Scimonster在评论中所说：循环引用不是无效的。