Checking for Object Immutability in JavaScript

Verifying Object Immutability with Object.isFrozen()

The Object.isFrozen() method enables you to check whether an object is completely immutable, meaning that none of its properties can be added, removed, or altered.

const book = {
    title: 'The Catcher in the Rye',
    author: 'J.D. Salinger',
}

Object.freeze(book);

console.log(Object.isFrozen(book)); // true

Use Cases

Object.isFrozen() is valuable when you need to confirm whether an object is entirely unchangeable. For instance, consider a configuration object for a web application:

const config = {
  theme: 'dark',
  language: 'en',
  mode: 'light',
};

Object.freeze(config);

// Checking if the 'config' object is frozen.
if (Object.isFrozen(config)) {
  console.log('The configuration is immutable.');
} else {
  console.log('The configuration can still be altered.');
}

By using Object.isFrozen(), you can ensure that an object remains unchanged, maintaining data integrity in your applications.