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<html><body><h1>JavaScript Object Properties</h1><h2>Accessing a Property with an Expression</h2><p id="demo"></p><script>const person = { firstName: "John", lastName : "Doe", age : 50};let x = "firstName";let y = "age";document.getElementById("demo").innerHTML = person[x] + " is " + person[y] + " years old.";</script></body></html>