Confusion over Gmail load

[Hamilton Turner]

Attached video shows the issue. I create a new option, add an alert to both head JS and body JS. I receive the same alert ~4 times from the head and about ~5 times from the body. Is it expected that we should write JS in these boxes that can be run over and over without any issues? What are the basic rules for this, using lots of functions and ensuring that you check before you do something like add / remove an item from the dom? 

[Ansel Santosa]

Minimalist injects your scripts into all frames, not just to top one. Gmail has a ton of iframes in it. You have to make sure you are in the right frame and stop executing if you're not.