<!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>