Why does changing color by using js doesn't work

Question

Why is this js code doesn't work
https://code.sololearn.com/W2BTjj3i2AS7/?ref=app
Note: this is my first code so it's quite ugly

Answer 1

Try to use
window.onload=()=>{

var p=document.getElementById("p");

p.style.backgroundColor="blue";
}

Answer 2

Your HTML contens load before the JavaScript so you have to write JavaScript code inside the window.onload function so your Javascript code will execute after loading HTML contents.

window.onload = function () {
//Your code
}

Answer 3

Thanks

Answer 4

#HrCoder sorry but can you explain why?

Answer 5

Use @ instead of #

Answer 6

Thank you HrCoder