JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="log"></pre>

JavaScript

function view(obj) {
    var arr = [];
    for (var i in obj) arr.push(i + ": " + obj[i]);
    document.getElementById("log").innerHTML += "{" + arr.join(", ") + "}\n";
}

var obj = {
    c: 3,
    b: 2,
    "1": "1"
};

view(obj);

obj.a = 1;
view(obj);

delete obj.c;
obj.c = 3;
view(obj);

obj["0"] = "0";
view(obj);

obj["0.5"] = "0.5";
view(obj);