Why doesn't my simple code work ?!

Question

This circle should move , but it is still static !
https://code.sololearn.com/WqdQnyM6Zh9L/?ref=app

Answer 1

I have made some corrections. Check this code and try to understand how it works
https://code.sololearn.com/WVxbZ9TAk3BM/?ref=app

Answer 2

ctx.arc(this.x,this.y,this.r,0,Math.PI*2,false);

Answer 3

Calviղ Thanks , but it made the ball disappear