Multiple JS files in Chrome Extension – how to load them?

UPDATE : This solution works only if you are using manifest V2.

You can also do this the extremely easy way that is described here:
https://developer.chrome.com/extensions/background_pages#manifest

{
  "name": "My extension",
  ...
  "background": {
    "scripts": [
      "lib/fileone.js",
      "lib/filetwo.js",
      "background.js"
    ]
  },
  ...
}

You won’t be doing lazy loading, but it does allow you to break your code up into multiple files and specify the order in which they are loaded onto the background page.