sololearn don't know canvas?

Question

this code runs perfectly outside sololearn,but sololearn fails to recognize the canvas element
https://code.sololearn.com/W7oqMjVW6rKS/?ref=app

Answer 1

Sololearn Javascript pane code is run from head tag before DOM elements loaded.

You can't run DOM access code directly there, set window.onload callback function instead.