Here is My code,
var myExtension = chrome.management.get( \"my_extention_id\" );
if (myExtension.enabled)
{
// installed
}
else { ... }
sou
https://gist.github.com/greatghoul/321b4f32c0b7a6ad8a97
https://developer.chrome.com/extensions/messaging#external-webpage
In manifest file, remember to register webpage you want to check extension from.
"externally_connectable": {
"matches": ["*://developer.chrome.com/*"]
}
then you can use chrome.runtime.sendMessage
in that page.