Unlocking the Power of Immutable Objects in JavaScript
The Importance of Object Immutability
In JavaScript, objects are mutable by default, which means they can be modified at any time. However, there are situations where you want to ensure that an object remains unchanged. This is where the Object.freeze() method comes into play.
What is Object Freeze?
Object.freeze() is a static method that freezes an object, preventing it from being modified. This means that once an object is frozen, you cannot add new properties, remove existing ones, or change the values of its properties.
How to Use Object Freeze
The syntax for Object.freeze() is straightforward: Object.freeze(obj), where obj is the object you want to freeze. For example:
const obj = { prop: 1, foo: 2 };
Object.freeze(obj);
What Happens When You Freeze an Object?
When you freeze an object, it becomes immutable. Any attempt to modify its properties or add new ones will fail silently or throw a TypeError in strict mode. Here’s what you can’t do with a frozen object:
- Add new properties
- Remove existing properties
- Change the enumerability, configurability, or writability of existing properties
- Change the values of existing object properties and prototypes
Key Differences Between Object Freeze and Object Seal
While both Object.freeze() and Object.seal() make objects immutable, there’s a key difference between them. Object.seal() allows you to change the values of existing properties, whereas Object.freeze() makes the existing properties immutable.
A Word of Caution
When using Object.freeze(), keep in mind that it only applies to the immediate properties of the object. If the values of those properties are objects themselves, they are not frozen and can still be modified.
Further Reading
If you’re interested in learning more about object immutability in JavaScript, check out Javascript Object.isFrozen() and JavaScript Object seal() methods.