Question

My goal is to create a button that when clicked deletes the parent divs on reddit whose links have already been visited. Due to security issues, visited link status cannot be detected from unprivileged javascript, thus, I attempted a chrome extension. However, this doesn’t seem to work either, as even the javascript called from an extension with history permission returns “Uncaught TypeError: Cannot call method ‘search’ of undefined.” Thus, I am still looking for a way to do this.

Update 1/8/2013

I’m very close to getting this working, however, I can’t get n_results in the content script to accurately reflect its status in the background script. Any ideas? Latest code below.

Update 1/8/2013

It’s working! See below if you need to do something like described above.

manifest.json

{
  "name": "Never The Same (NTS) Reddit",
  "version": "1.0",
  "manifest_version": 2,
  "description": "Previously visited links are deleted.",
  "browser_action": {"default_icon": "icon.png"},
  "permissions": ["history","tabs"],
  "content_scripts": [
      {
          "run_at": "document_end",
          "matches": ["http://www.reddit.com/*"],
          "js": ["jquery-1.8.3.min.js", "ntsreddit_content.js"]
      }
  ],
  "background": {"scripts": ["ntsreddit_background.js"]}
}

ntsreddit_background.js

chrome.extension.onMessage.addListener(
    function (request, sender) {
        chrome.history.getVisits({"url": request.url},
        function (visits) {
            if (visits.length > 0) {
                chrome.tabs.sendMessage(sender.tab.id, {
                    "url": request.url
                });
            };
        });
    });

ntsreddit_content.js

$("div.thing a.title").each(
    function(index, value) {
        chrome.extension.sendMessage({"url": value.href});
    });

chrome.extension.onMessage.addListener(function (message) {
    anchor=$('a[href^="' + message.url + '"][class~="title"]')
    if (anchor.length > 0) {
        anchor.closest(".thing").remove();
    };
});

Answer 1

Content scripts have some limitations. They cannot use chrome.* APIs (except for parts of chrome.extension), your code chrome.history in bookmarklet.js will always be undefined

EDIT:

After making some changes to your script i got it running.

Changes

• Chrome API(s) are asynchronous, you should only do further logical calculations after call back has returned
• sendResponse() Method is deprecated

ntsreddit_background.js

Moved tabs.sendMessage() to handle asynchronous nature of chrome API(s) and eliminated deprecated API(s)

chrome.extension.onMessage.addListener(

function (request, sender) {
    console.log(sender.tab);
    n_results = -1;

    console.log(request.link);

    chrome.history.getVisits({
        url: request.link
    },

    function (visits) {
        console.log(visits.length);
        n_results = visits.length;
        chrome.tabs.sendMessage(sender.tab.id, {
            "result": n_results
        });
    });



});

ntsreddit_content.js

Added a listener to handle response received from background Page

var firstlink = "https://www.google.co.in/";

chrome.extension.sendMessage({
    "link": firstlink
});
chrome.extension.onMessage.addListener(function (message, sender) {
    console.log(message.result);
});

I hope this solves your problem.