Chrome Extension: How to detect if an extension is installed using Content Scripts

Question

I am asking this question after looking at several related questions on stackoverflow. I started with how to detect if an extension is installed. I opted for the method wher

Answer 1

I got this working...

• Make the extension insert content script after DOM loads but before other resources like images are loaded

manifest.json (added "run_at": "document_end")

{
    "name": "Install Check",
    "content_scripts": [
        {
            "matches": ["http://host.com/*"],
            "js" : ["insert_node.js"],
            "run_at": "document_end"
        }
    ],
    "permissions": [
        "tabs", "host.com/*"
    ]
}

• use window.onload instead of $(document).ready

insert_node.js (changed the $(document).ready to window.onload)

window.onload = function() {
    if ($('#HOST_SITE').length > 0) {
        alert("you have our extension installed");
    } else {
        alert("not installed");
    }
};

However, I don't completely understand why using window.onload works and $(document).ready does not.

May be someone can shed some light on that?

Also I agree with @abraham that using chrome.app.isInstalled is a better way to do this (answer to my comment would be the icing on cake) :)

Answer 2

It looks like your own the extension and website, in which case it would be much easier to use Inline Installation.

if (typeof chrome !== "undefined" && typeof chrome.app !== "undefined" && chrome.app.isInstalled) {
  // extension is installed.
}

Answer 3

Im not sure how to do this with JQuery as $("#something") only seems to search the head and body?...and we need document.documentElement. Reason being that we are inserting something at document_start and there's no body/head then, but there is documentElement.

manifest.json

{
    "name": "Install Check",
    "content_scripts": [
        {
            "matches": ["HOST"],
            "js" : ["myscript.js"],
            "run_at":"document_start"
        }
    ],
    "permissions": [
        "tabs", "HOST"
    ],
    "version":"1.0"
}

myscript.js

var insert_node = document.createElement('div');
insert_node.id = "HOST_SITE";
document.documentElement.appendChild(insert_node);

notification.js

if (document.documentElement.querySelector("#HOST_SITE")) {
    alert("Installed");
} else {
    alert("Not Installed");
};