Modern frameworks rely on components and the shadow DOM. If you understand how these are implemented you'll go far.
One of the trickier things to grasp is where your CSS begins and ends. CSS is quite leaky here but there are ample style guides that illustrate pitfalls.
One of the trickier things to grasp is where your CSS begins and ends. CSS is quite leaky here but there are ample style guides that illustrate pitfalls.