JSFiddle - React, Tailwind, and code Playground

JavaScript

var d = document;
var cssId = 'test';
var allRules = [];

if (!d.getElementById(cssId))
{
    debugger;
    var head  = d.getElementsByTagName("head")[0];
    var link  = d.createElement("link");

  link.id   = cssId;

    link.rel  = "stylesheet";
    link.type = "text/css";
    link.href = "http://consolution.dk/d12/Daniel/test.css";
    link.media = "all";
    
    link.addEventListener('load', function(){
        var sheets = document.styleSheets,
            ourSheetOfInterest = null;
        
        debugger;
        
        // find our sheet
        for(var i=0; i<sheets.length; i++){
            if(sheets[i].ownerNode === link){
                ourSheetOfInterest = sheets[i];
            }
        }
        
        if( ! ourSheetOfInterest ){
            alert('couldn\'t find the link\'s stylesheet :(');
            return;
        }
        
        var rules = ourSheetOfInterest.cssRules;
        
        if( ! rules ){
            alert('rules was falsey');
            console.error('rules', rules);
            return;
        }
    
        for(var i = 0; i < rules.length; i++)
        {
            allRules.push(rules[i].selectorText);
            console.log(allRules[i]);
        }
        
    });
    head.appendChild(link);
}