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<!DOCTYPE html>
<html>
<body>
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<h2>JavaScript Object.keys()</h2>
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<p>This example list the enumerable properties of an object.</p>
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<p id="demo"></p>
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<script>
// Create an object:
const person = {
  firstName: "John",
  lastName: "Doe",
  language: "EN"
}
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// Change Property
Object.defineProperty(person, "language", {enumerable:false});
​
// Display Properties
document.getElementById("demo").innerHTML = Object.keys(person);
</script>
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</body>
</html>
​