JSFiddle - React, Tailwind, and code Playground

JavaScript

var Person = function() { 
    this.foo = function() {};
    // pozor, klíče zděděné z Object Internet Explorer for in ignoruje!
    // https://developer.mozilla.org/En/ECMAScript_DontEnum_attribute
    this.toString = function() {};
};
var joe = new Person();
for(var p in joe) alert(p);