JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div { height: 300px; background-color: blue;}

JavaScript

alert(css($('div')).background-color);


function css(a){
    var sheets = document.styleSheets, o = {};
    for(var i in sheets) {
        var rules = sheets[i].rules || sheets[i].cssRules;
        for(var r in rules) {
            if(a.is(rules[r].selectorText)) {
                o = $.extend(o, css2json(rules[r].style), css2json(a.attr('style')));
            }
        }
    }
    return o;
}

function css2json(css){
        var s = {};
        if(!css) return s;
        if(css instanceof CSSStyleDeclaration) {
            for(var i in css) {
                if((css[i]).toLowerCase) {
                    s[(css[i]).toLowerCase()] = (css[css[i]]);
                }
            }
        } else if(typeof css == "string") {
            css = css.split("; ");          
            for (var i in css) {
                var l = css[i].split(": ");
                s[l[0].toLowerCase()] = (l[1]);
            };
        }
        return s;
    }