Detect if window.close() will work before using it (JavaScript)

Question

According to many rules and security features, window.close() will only work in specific cases:

From the latest working spec for window.close():

The close() method on Window objects should, if all the following conditions are met, close the browsing context A:

• The corresponding browsing context A is script-closable.
• The browsing context of the incumbent script is familiar with the browsing context A.
• The browsing context of the incumbent script is allowed to navigate the browsing context A.

A browsing context is script-closable if it is an auxiliary browsing context that was created by a script (as opposed to by an action of the user), or if it is a browsing context whose session history contains only one Document.

I have a web application that allows users to close new windows and it works fine, except when the rules above are not respected.

What I am looking for is to detect when the close() function will work and only show the close button in such case.

I found information talking about window.opener that returns a reference from the window that opened it. But it doesn't work.

if(window.opener != null){
//show button
}

Maybe this is because the new window was opened using "right click -> open in new tab" and not a script. When tabs are opened in this fashion window.close() works, I just want to detect when window.close() will work.

Any ideas?

Answer 1

According to the docs, the window is script-closable also if session history of the given context is of length 1 (which is exactly what happens when you open a link in a new tab/window). You need to add that to your checker.

if(window.opener != null || window.history.length == 1){
//show button
}