外部スクリプトから Chrome 拡張機能のインストール ステータスを確認する方法

chrome.runtime.onMessageExternal.addListener(
    function(request, sender, sendResponse) {
        if (request) {
            if (request.message) {
                if (request.message == "version") {
                    sendResponse({version: 1.0});
                }
            }
        }
        return true;
    });

var hasExtension = false;

chrome.runtime.sendMessage(extensionId, { message: "version" },
    function (reply) {
        if (reply) {
            if (reply.version) {
                if (reply.version >= requiredVersion) {
                    hasExtension = true;
                }
            }
        }
        else {
          hasExtension = false;
        }
    });

"externally_connectable": {
    "matches": ["*://localhost/*", "*://your.domain.com/*"]
},

if (chrome.runtime.lastError) {
    // handle error
}