Mutable and Immutable Objects

What Are Mutable Objects?

Mutable objects are those whose state (values) can be modified after the object is created. This means you can update properties or elements of a mutable object, and those changes are reflected in the same object without creating a new instance.

Advantages of Mutable Objects

• Memory Efficiency: Mutable objects allow modifications in-place, which can save memory.
• Flexibility: They allow dynamic changes, making them suitable for scenarios that require frequent modifications.
• Performance: In some cases, modifying an existing object is faster than creating a new one.

Example: Mutable Objects

In JavaScript, objects and arrays are mutable by default:

let person = { name: "Alice", age: 25 };
person.age = 26;  // Modifying the object
console.log(person); // { name: "Alice", age: 26 }

What Are Immutable Objects?

Immutable objects, on the other hand, cannot be changed after creation. Any operation that seems to modify an immutable object actually creates a new object with the updated state instead of altering the original.

Advantages of Immutable Objects

• Predictability: Since values never change, there's less risk of unintended modifications and debugging becomes easier.
• Thread Safety: Immutable objects prevent race conditions in concurrent applications because their state can't change.
• Hashability: Since their values don't change, immutable objects can be used as keys in dictionaries or elements in sets.

Example: Immutable Objects

In JavaScript, primitive types such as string, number, and boolean are immutable:

let str = "Hello";
str[0] = "h";  // No effect
console.log(str); // "Hello"

To work with immutable objects in JavaScript, you can use Object.freeze() or spread operators to create a new object:

const obj = Object.freeze({ name: "Bob" });
obj.name = "Charlie";  // This won't change the object
console.log(obj.name); // "Bob"

When to Use Mutable and Immutable Objects

• Use Mutable Objects when performance and memory efficiency are critical, such as updating a large dataset frequently.
• Use Immutable Objects when maintaining state consistency is important, such as in functional programming or React state management.

By understanding when and where to use mutable and immutable objects, developers can write more efficient and predictable code.