Rails adblock JS file behaving differently in production / development

Question

I have a single file, ads.js located in my assets/javascripts folder in rails. It contains one line of code - canRunAds = true, which I query elsewhere in my app with the script below. If it returns undefined, I serve up an adblock message.

It works perfectly in development, when I'm testing it, and canRunAds will indeed return undefined. In production, however, with adblock turned on - it logs the message Adblock not detected - i.e. it doesn't work as expected. Weirdly, I also get Chrome telling me ERR_BLOCKED_BY_CLIENT for the ads.js file... so the file is being blocked, but canRunAds is still returning true, how?

I've precompiled my assets, and the ads.js file is definitely in there. My knowledge on how rails loads assets is limited enough that I don't know what to Google next to resolve this. Someone told me rails production will sometimes "reload & autoload all the things whenever" but that's all the info I have to go on...

Any help/pointers would be much appreciated!

    function detectAdblock(){
      if( window.canRunAds === undefined){
        console.log("Adblock detected")
        var donateBanners = document.getElementsByClassName("donations");
        for (i = 0; i < donateBanners.length; i++) {
            donateBanners[i].style.display = "block";
            console.log("Banner displayed! " + i)
        }
      }
      else {
        console.log("Adblock not detected");
      }
    }
    window.onload = detectAdblock;

Answer 1

Figured it out eventually.

It was working in development because rails was serving up static asset files like ads.js individually (so adblock picked up on the filename and blocked it). I think this is because the variable config.serve_static_files = true is set (whilst being false in production).

In production, the file contents were being shovelled into application.js so the filename wasn’t being picked up. I threw it into the public folder and that did the trick.