runtime.getBackgroundPage()

Retrieves the Window object for the background page running inside the current extension.

This provides a convenient way for other privileged extension scripts to get direct access to the background script's scope. This enables them to access variables or call functions defined in that scope. "Privileged script" here includes scripts running in options pages, or scripts running in browser action or page action popups, but does not include content scripts.

Note that variables that were declared using const or let do not appear in the Window object returned by this function.

Also note that this method cannot be used in a private window in Firefox—it always returns null. For more info see related bug at bugzilla.

If the background page is an event page, the system will ensure it is loaded before resolving the promise.

This is an asynchronous function that returns a Promise.

Syntax

var gettingPage = browser.runtime.getBackgroundPage()

Parameters

None.

Return value

A Promise that will be fulfilled with the Window object for the background page, if there is one. If the extension does not include a background page, the promise is rejected with an error message.

Browser compatibility

Examples

Suppose a background script defines a function foo():

// background.js

function foo() {
  console.log("I'm defined in background.js");
}

A script running in a popup can call this function directly like this:

// popup.js

function onGot(page) {
  page.foo();
}

function onError(error) {
  console.log(`Error: ${error}`);
}

var getting = browser.runtime.getBackgroundPage();
getting.then(onGot, onError);