JSFiddle - React, Tailwind, and code Playground

JavaScript

//Original definition
var foo = function(){};
foo.prototype.bar = function(){
    console.log( 'function says: Original Bar' ); 
};
foo.prototype.myName = "My name is Adam";

//Instantation
var fooInstance = new foo();

//Use Instantiation
fooInstance.bar(); //alerts 'Original Bar';
console.log( typeof fooInstance.someFunction ); //alerts 'undefined'

//Modify prototype
foo.prototype.bar = function(){ 
    console.log( 'Function now says New Bar' ); 
};
foo.prototype.someFunction = function(){};

//Use same instantiation
fooInstance.bar(); //alert 'New Bar';

console.log(fooInstance.myName);

foo.prototype.myName = "My name is Gilligan";

console.log(fooInstance.myName);

console.log( typeof fooInstance.someFunction ); //alerts 'function'