Вы это читали?
https://developer.chrome.com/extensions/content_sc...
Declaratively injected scripts are registered in the manifest under the "content_scripts" field. They can include JavaScript files, CSS files or both. All auto-run content scripts must specify match patterns.
{
"name": "My extension",
...
"content_scripts": [
{
"matches": ["http://*.nytimes.com/*"],
"css": ["myStyles.css"],
"js": ["contentScript.js"]
}
],
...
}
js
array of strings Optional. The
list of JavaScript files to be injected into matching pages. These are
injected in the order they appear in this array.
тоже самое и с секцией background
https://developer.chrome.com/extensions/background...
{
"name": "Awesome Test Extension",
...
"background": {
"scripts": [
"backgroundContextMenus.js",
"backgroundOmniBox.js",
"backgroundOauth.js"
],
"persistent": false
},
...
}
PS: в popup они вставляются через тег script как в обычном HTML файле.
