apply css with javascript code example

Example 1: add style javascript

// Bad:
element.setAttribute("style", "background-color: red;");
// Good:
element.style.backgroundColor = "red";

Example 2: 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");