Examples for front-end dev (CSS/HTML/JS)
Uncleared float causing a collapse, collapsing margins, poor selector priority or confused about why X has priority over Y. Div soup structure with unnecessary divs/floats to attain desired layout. Off-by-one errors in Javascript (without being able to identify it) or not being able to identify when they are out-of-scope or what `this` is referencing.
Once they stop making silly mistakes they become a `developer'` At which point the kinds of mistakes they are making are less trivial and occasionally overlap with problems `senior developer` have. But they can confidently debug and generally solve their own problems so require less attention from other devs.
Everybody sometimes makes stupid bugs and doesn't see why. Everybody sometimes doesn't know obvious things. Everybody is beginner sometimes. I think that even when senior programmer learns new approach, new project, new language, new paradigm, new tool etc. is as confused as beginner.
I think senior/middle/junior are just hierarchy markers to:
- define your salary
- define your responsibilities in project/company
- boost your ego (senior), or keep you to stay humble (junior)
"At which point the kinds of mistakes they are making are less trivial and occasionally overlap with problems `senior developer` have."
I don't know what you mean. I think every developer in a team is often experiencing similar problems. For example architecture, code quality. You could say that only seniors must be thinking about this. But this is not true, because when there is spaghetti code in project - whole team has this problem. Even junior developer has to deal with spaghetti code (for example), even if he is not experienced enough to write clean code (or even he made this code himself xD).
Besides the biggest problems in development are often not technical ones but more people/management related ones. It doesn't really matter if developers are good or bad, if the project or team is poor managed, or if there are some communication issues.
If a senior developer remains stagnant, they'll quickly fall behind.