JSFiddle - React, Tailwind, and code Playground

HTML

<a id="test">test anchor tag</a>

CSS

a {color: red;}
a:hover {color: blue;}

JavaScript

function getCssPropertyForRule(rule, prop) {
    var sheets = document.styleSheets;
    var slen = sheets.length;
    for(var i=0; i<slen; i++) {
        var rules = document.styleSheets[i].cssRules;
        var rlen = rules.length;
        for(var j=0; j<rlen; j++) {
            if(rules[j].selectorText == rule) {
                return rules[j].style[prop];
            }
        }
    }
}


alert("Hovered Colour is "+getCssPropertyForRule('a:hover', 'color'));