JSFiddle - React, Tailwind, and code Playground

JavaScript

(function () { 
    var myGlobal = {
        prop1: "hello"
    };

    function myGlobalFunc() {
        return "world";
    };

    Object.defineProperties(window,
        {
            myGlobal: {
                get: function () {
                    return myGlobal;
                }
            },
            myGlobalFunc: {
                get: function () {
                    return myGlobalFunc;
                }
            }
        }
    );
})();

$("body").append($("<script>").text('var myGlobal = {    prop1: "goodbye"};function myGlobalFunc() {    return "universe";};'));

alert(myGlobal.prop1 + " " + myGlobalFunc()); // displays "hello world"