Why won't canvas work?

Question

So i just found out about the valentines coding completion and so I started my code and made this empty rectangle but it's giving me an error. Can someone help?

https://sololearn.com/compiler-playground/Wvta0PI3yzEa/?ref=app

Answer 1

onload =()=>{

let canvas = document.getElementById("letter");
let ctx=canvas.getContext("2d")
ctx.fillStyle="white";
ctx.fillRect(50,100,200,200);

}

Answer 2

I solved it already but thanks