If you can write javascript that solves problems you are a software engineer. Your skill level will vary in comparison to other people but there is no reason you can't call yourself a software engineer.

If you want continue to increase your skill level then the best way is to start branching out in the set of tools you can comfortably use. Write a small API server, Create some command line utilities for yourself, learn some different programming languages.

On each new think increase the difficulty level a bit. Push yourself, you'll continue to grow and your skill level will continue to vary in comparison to other because of it.