It was good to be able to become more familiar with how to use TypeScript. In particular, I was able to fully understand the situation where I need to use type assertions because it was explained in relation to DOM. One thing that was disappointing was that after the date of uploading the lecture, chartjs started supporting types, and the lecture content changed slightly, causing errors. It is not difficult to learn how to use TypeScript, so I think it would be good for others to listen to it as well.