how to create a css variable js code example
Example 1: how to change a css variable with javascript
var root = document.querySelector(':root');
root.style.setProperty('--variable', 'lightblue');
/or/
root.style.setProperty('--variable', myColor);
Example 2: javascript get css variable
let docStyle = getComputedStyle(document.documentElement);
//get variable
let myVarVal docStyle.getPropertyValue('--my-variable-name');
//set variable
docStyle.setProperty('--my-variable-name', '#fff');