An immutable object is a data structure that cannot be modified after it is created. Instead of changing values directly, operations on immutable objects create new versions with the updated data. Immutable structures are common in functional programming and help eliminate side effects, making code easier to reason about and test.
Why it matters
Immutable objects simplify concurrency, prevent accidental mutations, and reduce bugs caused by shared state. They are essential in frameworks like React, which rely on immutability to detect changes and trigger UI updates efficiently.
Examples
Strings in many languages are immutable. Libraries like Immutable.js and language features in Rust or Clojure enforce immutability. Lessons on state—such as State Management Concepts—explain why immutability matters.