JSFiddle - React, Tailwind, and code Playground

JavaScript

window.getUrlParameter = (function() {
    var startBracketRe = /[\[]/,
        endBracketRe   = /[\]]/,
        regexes        = {};
    
    return function (name) {
        name = name.replace(startBracketRe, '\\[').replace(endBracketRe, '\\]');
        
        var regex   = regexes[name] || (regexes[name] = new RegExp('[\\?&]' + name + '=([^&#]*)')),
            results = regex.exec(location.search);
            
        return results === null ? '' : decodeURIComponent(results[1].replace(/\+/g, ' '));
    };
})();

var dc = getUrlParameter('_dc');

console.log(dc);