Answers for "how to make css var with javascript"

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");

how to set css variables in javascript

const docStyles = document.documentElement.style;

		docStyles.setProperty('--accent', '#ffffff');
		docStyles.setProperty('--textColor', '#ffffff');