JSFiddle - React, Tailwind, and code Playground

JavaScript

//+ fn -> [a]
var getParameterNames = (function () {
    var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg,
        ARGUMENT_NAMES = /([^\s,]+)/g;
 
    return function (fn) {
        var fnStr = fn.toString().replace(STRIP_COMMENTS, ''),
            names = fnStr.slice(fnStr.indexOf('(')+1, fnStr.indexOf(')')).match(ARGUMENT_NAMES);
 
        return names || [];
    };
})();
 
function add (x, y) {
    return x + y;
}
 
document.body.innerHTML = getParameterNames(add);    // => ['x', 'y']