detect if Chrome extension content script has been injected / content script include guard

Question

I want to execute a content script function whenever a tab is updated. The problem is that, sometimes the tab update is ajax (without a page reload), while still changing th

Answer 1

Implementing an include guard is extremely easy:

(function() {
    if (window.hasRun) return;
    window.hasRun = true;
    // Rest of code
})();

If you want to programatically inject a content script, consider using one of the webNavigation events (e.g. onCommitted) instead of chrome.tabs.onUpdated. Unlike the tabs events, the webNavigation events are also triggered for navigation within frames, and offer a way to declare an URL filter in advance.