JSFiddle - React, Tailwind, and code Playground

JavaScript

function _addEvent(e, evt, handler){
    if(evt == "ready")
        evt = "DOMContentLoaded";
    
    if(typeof handler !== 'function')return;
    if (e.addEventListener)
        e.addEventListener(evt, handler, false);
    else if (e.attachEvent)
        e.attachEvent("on" + evt, handler);
    else
    {
        var oldHandler = e["on" + evt];   
        function newHandler(event){
            handler.call(e, event);
            if(typeof oldhandler === 'function')oldhandler.call(e, event);
        }
    }
}
var _events = ["ready", "click", "mousedown"]; //...
var _myLib = function(item){
    function eventWorker(item, event){
        this.add = function(handler){
            _addEvent(item, event, handler);
        };
    }
    for(var i=0;i<_events.length;i++)
        this[_events[i]] = (new eventWorker(item, _events[i])).add;
};
var MyLib = function(item){
    return new _myLib(item);
};
    
    MyLib(document).ready(function(){alert("I am ready!");});