JSFiddle - React, Tailwind, and code Playground

HTML

<a href="#">Hover 1</a>
<a id="link" href="#">Hover 2</a>

CSS

a:hover{
    color:green;
}
#link:hover{
    color:red;
}

JavaScript

function getStyleBySelector( selector )
   {
       var sheetList = document.styleSheets;
       var ruleList;
       var i, j;
   
       /* look through stylesheets in reverse order that
          they appear in the document */
       for (i=sheetList.length-1; i >= 0; i--)
       {
           ruleList = sheetList[i].cssRules;
           for (j=0; j<ruleList.length; j++)
           {
               if (ruleList[j].type == CSSRule.STYLE_RULE && 
                   ruleList[j].selectorText == selector)
               {
                   return ruleList[j].style;
               }   
           }
       }
       return null;
   }

console.log(getStyleBySelector('a:hover').color);
console.log(getStyleBySelector('#link:hover').color);