JSFiddle - React, Tailwind, and code Playground

HTML

<div class="button_48x49_img button_join_login_48x49_img"></div>

CSS

.button_48x49_img {
    width: 48px;
    height: 49px;
}

.button_join_login_48x49_img {
    background-image: url('a.png');
}

.button_join_login_48x49_img:hover {
    background-image: url('b.png');
}

.button_join_login_48x49_img:active {
    background-image: url('c.png');
}

JavaScript

function getCssProperty(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];
            }
        }
    }
}


console.log(getCssProperty('.button_join_login_48x49_img:hover', 'background-image'));
console.log(getCssProperty('.button_join_login_48x49_img:active', 'background-image'));