First understanding would be of modules. Modules are used to import/pieces of code into another file. Without modules there would be no framework because it allows everything to be brought together.
- structuring a class
- methods and properties
- expending classes
Arrow functions is the modern standard in JS. Looks cleaner and less lines of code.
Also an understanding of promises/ asynchronous requests. The prerequisite suggestions were learn how to create and receive promises. Standard .then() and .catch() syntax. Lastly learn the fetch API for making HTTP requests.
Another prerequisite was to understand destructuring. It unpacks values from objects and arrays. Commonly used in frameworks and is cleaner code.
Finally an understanding the concept of components & state. UIs are broken up into individual components of which have some sort of state associated with them. Each component can have it’s own data & state of being. We also have application level state, usually implemented using a state manager like Redux, Vuex, etc. Nested components of parents and children.