As you do more independent projects with given language it becomes more impressive even if it were only 6 months of experience. If you get an interview and anyone asks how long you've been using the language be honest, but don't offer that until they ask. They may not care.
Years of experience is difficult to measure. If I have a node.js build script that I update occasionally, do I have one year of node.js experience after working on the project for a year?
A pure front-end developer will know Javascript much better than a back-end dev who started using it at the same time.
I also spent 3 years working with MySQL before actually learning to use joins or grouping.
Doing several independent project instead of a large one only makes it more impressive, but doesn't indicate greater skill.
Sometimes I wonder if I should add small half-baked projects to my portfolio. I may only have worked on them for two days, but they would make me look super prolific. Do you think that's a good idea?
Marketing isn't about painting an objective picture, your interviewers will be critical enough to balance it out. Don't do their job for them.