JSFiddle - React, Tailwind, and code Playground

HTML

<code id="test"></code>

JavaScript

var 
    ref = $("#test"),
    addtest = function(text1, text2) {
        ref.append("<span><b>'"+text1+"'</b>&nbsp;:&nbsp;"+text2+"</span><br />");
    };

var a, b = 0, c = "hola mundo";


addtest("void 0", void 0);
addtest("undefined == void 0", undefined == void 0);
addtest("a == void 0", a == void 0);
addtest("a == undefined", a == undefined);
addtest("b == void 0", b == void 0);
addtest("b == undefined", b == undefined);
addtest("c == void 0", c == void 0);
addtest("c == undefined", c == undefined);