document.documentElement.setAttribute("style", "--main-background-color: green");
document.documentElement.style.setProperty("--main-background-color", "green");
document.documentElement.style.cssText = "--main-background-color: red";
document.getElementById("myText").className = "anyNewClass"
let root = document.documentElement; root.addEventListener("mousemove", e => { root.style.setProperty('--mouse-x', e.clientX + "px"); root.style.setProperty('--mouse-y', e.clientY + "px"); });