I have been studying JS for 6 months now I believe, and I am far from done. Actually I believe that no one is ever done because there is soo much and new things keep coming. But that shouldn't be seen as a discouraging fact! This should get you excited! Because if there is one thing I learning in my one year of coding is that if you are not passionate about learning, coding is not for you. There is ALWAYS something new to learn and to improve, so yey, learning is awesome!
That being said, don't wait until you mastered 100% of concept to do a project or start learning a new one, because dude, mastering anything is almost impossible especially without getting to use it, so go code!!!