var clone = require("clone"); var today = new Date(); var todayCloned = clone(today); var console = require("jquery")("<pre/>").appendTo('body'); console.append ( "Is todayCloned is an instance of Date? – " + (todayCloned instanceof Date ? "Yup!" : "Nope.") + "\n" ); Date.prototype.justInserted = "This has just been inserted to Date's prototype." console.append(todayCloned.justInserted + "\n");