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<!DOCTYPE html>
<html>
<body>
<h2>Using JavaScript Symbol()</h2>
<p id="demo"></p>
<script>
const person = {
  firstName: "John",
  lastName: "Doe",
  age: 50,
  eyeColor: "blue"
};
let id = Symbol('id');
person[id] = 140353;
document.getElementById("demo").innerHTML = person[id] + " " + person.id;
</script>
</body>
</html>