Why is the output null instead of the div element?

Question

Something seems be wrong with my sololearn editor. Any reference I make to an HTML element in JavaScript outputs null. I don't know why. I'm not able to upload any of my recent codes because of this. Please help.

https://code.sololearn.com/WgC6NwEWg4J1/?ref=app

Answer 1

Recently, I also had some problems with a JS code on my SL Playground. The code is saved as code bits. When I try some loops, the Playground blocks. I need to restart SL mobile app.

I tried this code in your file and there is an error, so there are some problems:

var demo = document.getElementById("demo");
demo.innerHTML = "test";
//console.log(demo);

Answer 2

window.onload = ()=>{
const demo = document.querySelector('#demo')
console.log(demo)
}