52. What is the purpose of the delete operator?

In JavaScript, the delete operator is used to remove a property from an object. If the property is successfully deleted, it returns true; otherwise, it returns false.

Syntax:

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delete object.property;
delete object['property'];

How It Works:

1. The delete operator works on object properties, not on variables or function names.
2. If the property exists and is deleted, it returns true.
3. If the property does not exist, it returns true (because there’s nothing to delete).
4. If the property is marked as non-configurable (like properties of built-in objects), it returns false.

Example 1: Deleting an object property

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const person = {
  name: 'John',
  age: 30
};

console.log(person.age); // 30

delete person.age; // Deletes the 'age' property

console.log(person.age); // undefined

Example 2: Trying to delete a non-configurable property

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const obj = {};
Object.defineProperty(obj, 'name', {
  value: 'John',
  configurable: false // Property is non-configurable
});

console.log(delete obj.name); // false
console.log(obj.name); // 'John'

Example 3: Deleting an array element

If you use delete on an array element, it creates an empty slot instead of shifting the elements:

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const arr = [1, 2, 3];
delete arr[1];

console.log(arr); // [1, empty, 3]
console.log(arr.length); // 3

Key Points:

• delete only works on object properties.
• It doesn’t affect the length of an array.
• Deleting a variable declared with var, let, or const does not work:

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var x = 10;
delete x; // false
console.log(x); // 10