Answers for "how to get js variable value in css"

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');

javascript get css variable

getComputedStyle(document.documentElement)
    .getPropertyValue('--my-variable-name'); // #999999