Object property descriptors in JavaScript (writable, enumerable, configurable)

In JavaScript, every property on an object has a set of hidden attributes known as property descriptors. These control how the property is stored, modified, or displayed in the object.

There are three main descriptors: writable, enumerable, and configurable. To access or modify these properties, we use the Object.defineProperty() method.

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1. writable — Whether the value can be changed

  
const person = {};
Object.defineProperty(person, 'name', {
  value: 'Anna',
  writable: false
});

person.name = 'Mariam';
console.log(person.name); // 'Anna'
  

Advantages of this property:

• You can prevent the value from ever being changed
• Useful for creating readonly properties

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2. enumerable — Whether the property is visible in loops

  
const user = {};
Object.defineProperty(user, 'id', {
  value: 101,
  enumerable: false
});

for (let key in user) {
  console.log(key); // prints nothing
}

console.log(Object.keys(user)); // []
  

Advantages of this property:

• Hides properties from `for...in` and `Object.keys()`
• Useful for internal/private data

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3. configurable — Whether the property can be deleted or reconfigured

  
const settings = {};
Object.defineProperty(settings, 'theme', {
  value: 'dark',
  configurable: false
});

delete settings.theme;
console.log(settings.theme); // 'dark'

Object.defineProperty(settings, 'theme', {
  value: 'light'
}); // Error in strict mode
  

Advantages of this property:

• You can lock properties to prevent their redefinition or deletion
• Useful when you need to enforce security on an object

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How to view a property's descriptor

  
const car = { brand: 'Toyota' };

const descriptor = Object.getOwnPropertyDescriptor(car, 'brand');
console.log(descriptor);

// {
//   value: 'Toyota',
//   writable: true,
//   enumerable: true,
//   configurable: true
// }
  

Advantages of this method:

• You can see all three main flags
• Useful for debugging and object analysis

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