I'm using Microsoft Edge in localhost for development.
Website is accessed via http://localhost
I open a popup and want it to post a message to the opener via window.opener.postMessage
My code works with Chrome, and Safari, and even Microsoft Edge when the website is on staging or production.
But when I run in in local mode, the window.opener is undefined.
CORS on localhost is tricky so try to create a domain name you like to your hosts file (%windir%\System32\Drivers\etc\hosts) - if you're in a Windows-based platform and map those back to 127.0.0.1.
You probably already know how to change the hosts file but just in case:
http://support.hostgator.com/articles/general-help/technical/how-do-i-change-my-hosts-file
Microsoft Edge runs in network isolation and does not currently support localhost testing. Run this in an elevated command prompt to enable loopback support:
CheckNetIsolation LoopbackExempt -a -n=Microsoft.MicrosoftEdge_8wekyb3d8bbwe
In a future update, you’ll be able to enable localhost loopback support using about:flags.
More info: http://dev.modern.ie/platform/faq/how-can-i-debug-localhost/
来源：https://stackoverflow.com/questions/31196295/window-opener-in-microsoft-edge-undefined-when-running-at-localhost