JSFiddle - React, Tailwind, and code Playground

JavaScript

var Animal = function() {

  this.sound = "";
  this.talk = function(){
      console.log(this); 
      console.log(this.sound);
  };

};

var dog = new Animal();
dog.sound = "Woof";
dog.talk(); //Woof as expected

var cat = $.extend(true, {}, dog); 
cat.sound = "Meow";
cat.talk(); //Woof... but Meow was expected