CODEWITHSUNDEEP
javascriptwindow
lukehillonline
lukehillonline

Reputation: 2647

JavaScript: What's the difference between window.top and top.window

I have been recently been reading into the JavaScript top functionality and noticed that I can run either window.top or top.window. From what I can see there is no difference in functionality so it seems to be strange that it is possible to run both.

// They appear to be the same here at least:
console.log(window.top === top.window);

MDN documentation

My question is, does anyone know why this functionality exists twice and are there any differences between the two? I am wondering about things like differences in browser support, or quirky bugs related to running it one way or another.

Upvotes: 3

Views: 1419

Answers (1)

CertainPerformance
CertainPerformance

Reputation: 370799

window is the global object, so properties on it can be accessed as if they were standalone variables. So referencing top on the top level is the same as referencing window.top. So the question boils down to the difference is between

window.top

and

window.top.window

window.top gives you a window object (it may be the same as window, or it may be an outer window, if you're in an iframe), and a window's window property is a reference to the same window object (it's a weird self-reference), so those two references are exactly the same as well. You can count on

window.top === window.top.window

to always be true.

Upvotes: 6

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