Check if window was opened by script in JavaScript

Question

Is it possible to check if script opened a window with JavaScript?

I have User agreements and they are opened in a new window and when I try to close the window, this works:

<a href="JavaScript:window.close()" class="btn btn-default">Return</a>

But what I would like to accomplish is that if the user go directly to /agreeement and clicks close, that it redirects him to the homepage.

Using my current code in this case, I get a message:

Scripts may close only the windows that were opened by it.

And I understand why. That is why I would like to check whether the window was not opened from a script, and then redirect to index in that case.

Answer 1

window.opener will be null when the page is not opened by another window, and therefore can not be closed.

This code should should do the trick:

function goAway() {
    if(window.opener === null) {
        window.location.href = '<YOUR_DEFAULT_URL>';
    }
    else {
        window.close();
    }
}

You can find more details here