should you use li or div for css grid code example

Example 1: how do i make a div full width with css

.row-full{
 width: 100vw;
 position: relative;
 margin-left: -50vw;
 height: 100px;
 margin-top: 100px;
 left: 50%;
}

Example 2: do some css using js on selector

let myElement = document.querySelector("#superman");
myElement.style.backgroundColor = "#D93600";