Developing Frontend Skills Through Side Projects

About 2 months ago, I got an offer to help my friend in working on one of his projects related to managing ISP services. Since he only asked me to work on the frontend-side and he gave me full responsibility to chose the technology I was using, I decided to use React and Typescript to work on the project.

At that time, I could complete the project prototypes pretty quickly. But, considering the time allotted to make the prototype is still quite long, I decided to use the new technology from React which is the context API and React Hooks which recently released the stable version. Unfortunately, the project is currently on-hold at the request of the client. Therefore, I need to find new things that I can do to get more knowledge and to be used as a portfolio for my resume. Do you have any suggestions for projects that I can work on?