Can the window object be modified from a Chrome extension?

Question

I would like to make a Chrome extension that provides a new object inside window. When a web page is viewed in a browser with the extension loaded, I would like

Answer 1

A chrome extension's content_script runs within its own context which is separate from the window. You can inject a script into the page though so it runs in the same context as the page's window, like this: Chrome extension - retrieving global variable from webpage

I was able to call methods on the window object and modify window properties by essentially adding a script.js to the page's DOM:

var s = document.createElement('script');
s.src = chrome.extension.getURL('script.js');
(document.head||document.documentElement).appendChild(s);
s.onload = function() {
    s.remove();
};

and creating custom event listeners in that injected script file:

document.addEventListener('_my_custom_event', function(e) {
  // do whatever you'd like! Like access the window obj
  window.myData = e.detail.my_event_data;
})

and dispatching that event in the content_script:

var foo = 'bar'
document.dispatchEvent(new CustomEvent('_save_OG_Editor', {
  'detail': {
    'my_event_data': foo
  }
}))

or vice versa; dispatch events in script.js and listen for them in your extension's content_script (like the above link illustrates well).

Just be sure to add your injected script within your extension's files, and add the script file's path to your manifest within "web_accessible_resources" or you'll get an error.

Hope that helps someone \ (•◡•) /