JSFiddle - React, Tailwind, and code Playground

CSS

p {
    color: red;
}

JavaScript

getStyle = function (el, prop) {
    if (getComputedStyle !== 'undefined') {
        return getComputedStyle(el, null).getPropertyValue(prop);
    } else {
        return el.currentStyle[prop];
    }
}

// Create paragraph element and append some text to it
var p = document.createElement('p');
p.appendChild(document.createTextNode('something for fun'));

// Append element to the body
document.getElementsByTagName('body')[0].appendChild(p);

// Set hex color to this element
p.style.color = '#f99';

// alert element's color using getStyle function
alert(getStyle(p, 'color'));