JSFiddle - React, Tailwind, and code Playground

JavaScript

MyClass = (function() {
  var defaults = {
    myArr: [],
    myProp: 'I\'m a default value'
  };

  function MyClass(options) {
    // console.log(defaults)
    if(typeof options === 'object') {
      return _.extend(this, _.cloneDeep(defaults), options);
    }
    else {
      return _.extend(this, defaults);
    }
  }

  return MyClass;
})();

var myObj = new MyClass({foo: 'bar'})
myObj.myArr.push('baz')
var mySecondObj = new MyClass();
console.log(myObj) // MyClass {myArr: Array[1]}
console.log(mySecondObj) // MyClass {myArr: Array[1]}