@james Independent implementation, novel problem solving, and ambiguity resolution, and communication, I think.
More specifically, a plurality of the following:
- Being able to characterize a problem so someone else can follow along (bug reports, asking for help online, etc)
- Being able to dive into unfamiliar tech
- Intermediate research ability (not just Google or GPT, but also digging into docs or source as available/needed)
- A growing intuition for unclear requirements, and being able to resolve them
- Exposure to JS without frameworks
- Ability to produce clear prose
- Ability to build layouts via CSS
- Ability to troubleshoot bundler errors
- Growing understanding of version control
(And, of course, by a plurality, I don't expect most mid levels to have all of those, but they should have somewhere around half, and my list is probably incomplete)