One important thing is a final web page is a confluence of code coming from different sources, and not controlled by the end user or the developer/website. If y

One important thing is a final web page is a confluence of code coming from different sources, and not controlled by the end user or the developer/website. If you define some functionality, I could just override (intentionally or not) with my code which also gets loaded along with yours. Combine this with the inconsistent browser playground, you might get some perspective of the hacky nature of the workings in the front end world.