Answers for "js update css variable"

how to change a css variable with javascript

var root = document.querySelector(':root');
root.style.setProperty('--variable', 'lightblue');
/or/
root.style.setProperty('--variable', myColor);

how to change css variable in javascript

document.documentElement.style.setProperty("--main-background-color", "green");

set css variable from javascript

document.documentElement.style.cssText = "--tab-count: 3";
/or/
document.documentElement.style.setProperty("--tab-count", 5);
/or/
document.documentElement.setAttribute("style", "--tab-count: 5");

change css variable with javascript

let root = document.documentElement;

root.addEventListener("mousemove", e => {
  root.style.setProperty('--mouse-x', e.clientX + "px");
  root.style.setProperty('--mouse-y', e.clientY + "px");
});