Clona uma variável em javascript

clone.js

let clone = function(obj) {
  let copy;

  // Handle the 3 simple types, and null or undefined
  if (null === obj || "object" !== typeof obj) return obj;

  // Handle Date
  if (obj instanceof Date) {
    copy = new Date();
    copy.setTime(obj.getTime());
    return copy;
  }

  // Handle Array
  if (obj instanceof Array) {
    copy = [];
    for (let i = 0, len = obj.length; i < len; i++) {
      copy[i] = clone(obj[i]);
    }
    return copy;
  }

  // Handle Object
  if (obj instanceof Object) {
    copy = {};
    for (let attr in obj) {
      if (obj.hasOwnProperty(attr)) copy[attr] = clone(obj[attr]);
    }
    return copy;
  }

  return JSON.parse(JSON.stringify(obj));
};