Chrome Extension: using document.querySelector in background script

问题

I'm trying to set a variable equal to the favicon url of the current page. Are you not able to do this in the background script? How else could I get the current page's favicon url that the user is on?

background.js

var currentFaviconURL = document.querySelector("link[rel*='shortcut icon']").href;
console.log(currentFaviconURL);

console

Error in response to tabs.query: TypeError: Cannot read property 'href' of null

回答1:

For reading and manipulating DOM, you must use Content Scripts. https://developer.chrome.com/extensions/content_scripts

来源：https://stackoverflow.com/questions/51885877/chrome-extension-using-document-queryselector-in-background-script