Depending on the company size and your aptitude, you might get called on to do user research, compile those into user stories, and then wireframe, and then make screens i.e. UI/UX design.
You should be able to interact with APIs, e.g. make a GET request to the server and handle that data.
You may be called on to optimize algorithms, for example drawing a table with a large amount of data.
You should be able to read and use front-end CSS frameworks e.g. Bootstrap.