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<!DOCTYPE html> <html> <body> <p>You can add new properties to existing objects.</p> <p id="demo"></p> <script> var person = { firstname:"John", lastname:"Doe", age:50, eyecolor:"blue" }; person.nationality = "English"; document.getElementById("demo").innerHTML = person.firstname + " is " + person.nationality + "."; </script> </body> </html>