How to debug Google Chrome background script?

Question

I have very simple extension:

manifest.json

{
  "name": "historyCleaner",
  "version": "0.1.1",
  "manifest_version": 1,
  "description": "This is my first Chrome extension",
  "background": {
    "scripts": ["cleaner.js"]
  }, 
  "permissions": [
    "history"
  ]
}

cleaner.js

chrome.history.onVisited.addListener(function(HistoryItem result) {

  console.log("it works!");
  alert("it works!");

});

I've loaded it in Google Chrome, it is turned on and... it doesn't work. It doesn't log anything in console, it doesn't alert anything and what is worse, I can't find it in developers tools "Scripts" tab. How can I find why it doesn't work?

//edit

I've changed manifest.json to this one:

{
  "name": "historyCleaner",
  "version": "0.1.5",
  "manifest_version": 1,
  "description": "This is my first Chrome extension",
  "background_page": "background.html",
  "permissions": [
    "history",
    "background"
  ]
}

And embeded JavaScript in background.html

First you can try remove `HistoryItem` from first line - you have syntax error — hamczu, Apr 10 '12 at 01:35
Oh, I'm fool, I pasted it from documentation and forget about that:). But it still doesn't work. — ciembor, Apr 10 '12 at 01:46

Derek 朕會功夫 · Answer 1 · 2014-02-20T20:53:03.123

115

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and also if your console.log("it works!"); does not show up, then that's mean chrome.history.onVisited is not fired yet.

ps: For function(HistoryItem result), you may want to change it to function(result).

edited Feb 20 '14 at 20:53

answered Apr 10 '12 at 01:35

Derek 朕會功夫

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There is no "active script" near my extension:(. – ciembor Apr 10 '12 at 01:47
For example your "background.html":). In Polish Chrome it is named "Zobacz aktywne" what means "See/watch active". – ciembor Apr 10 '12 at 01:50
Maybe you should use HTML for easy debugging ;) When finish debugging, you could just change `.html` to `.js` (with little modification) – Derek 朕會功夫 Apr 10 '12 at 01:52
I've changed it into html, added all html tags, changed extension in manifest.json - no result. – ciembor Apr 10 '12 at 01:56
Did you check the `developer mode` at the top of chrome://extensions? (Extensions page) – Derek 朕會功夫 Apr 10 '12 at 02:02
Yes, it's turned on (it displays background.html of Adblock). – ciembor Apr 10 '12 at 02:09
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/9885/discussion-between-derek-and-ciembor) – Derek 朕會功夫 Apr 10 '12 at 02:11

StackRover · Answer 2 · 2012-07-04T00:21:20.593

This response might be late but would help the rest. if your background.html has javascript errors then the page will not load (to inspect).

To find out whats wrong with your background.html, under chrome://chrome/extensions/ (i.e., manage extensions), click on the background.html link. This will load the developer tools but without background.html. At the botton-right of the window, you will see a red error symbol, and clicking on it will provide line numbers that needs to be fixed.

How to debug Google Chrome background script?

2 Answers2

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