[javascript] Chrome Extension: Make it run every page load

I want to make a chrome extension that executes some scripts after one page is loaded, I am not sure whether I have to implement this logic on the background page or it can be anywhere else, any help here will be greatly appreciated.

This code should do it:

manifest.json

   {
      "name": "Alert 'hello world!' on page opening",
      "version": "1.0",
      "manifest_version": 2,
      "content_scripts": [
        {
          "matches": [
            "<all_urls>"
          ],
          "js": ["content.js"]
        }
      ]
    }

content.js

alert('Hello world!')

If it needs to run on the onload event of the page, meaning that the document and all its assets have loaded, this needs to be in a content script embedded in each page for which you wish to track onload.

You can put your script into a content-script, see

• content-script