Answers for "how to duplicate object with functions"

copy object javascript

var x = {key: 'value'}
var y = JSON.parse(JSON.stringify(x))

//this method actually creates a reference-free version of the object, unlike the other methods
//If you do not use Dates, functions, undefined, regExp or Infinity within your object

javascript clone object

let clone = Object.create(Object.getPrototypeOf(obj), Object.getOwnPropertyDescriptors(obj));