JSFiddle - React, Tailwind, and code Playground

CSS

.highlight{color: red;}

JavaScript

function findProperty(selector) {
        rules = document.styleSheets[1].cssRules
        for(i in rules) {
            if(rules[i].selectorText==selector) return rules[i].style.color;
        }
        return false;
    }
console.log(findProperty('.highlight'));