Immutable.js
Persistent immutable data structures for JavaScript — List, Map, Set, Record, Stack, OrderedMap, OrderedSet. Operations return new instances rather than mutating originals, with structural sharing for memory efficiency. Designed for React/Redux state management where immutability enables efficient change detection. Created by Facebook. TypeScript-first in v4+.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
MIT licensed. Immutability by design prevents mutation-based security bugs. No network, no external dependencies.
⚡ Reliability
Best When
You have deeply nested state in Redux with frequent updates where structural sharing provides measurable performance benefits and mutation safety is critical.
Avoid When
You're building simple React state or can use Immer (which provides immutability with mutable syntax on plain JS objects). Immer has largely superseded Immutable.js for most use cases.
Use Cases
- • Manage complex nested state in Redux applications where structural sharing prevents unnecessary re-renders
- • Build agent state machines where each state transition produces a new immutable state without mutation bugs
- • Implement undo/redo functionality by preserving previous immutable state versions cheaply via structural sharing
- • Process large datasets functionally in agent pipelines where mutation safety is critical for correctness
- • Create thread-safe (conceptually) shared state in complex agent architectures where mutation causes race conditions
Not For
- • Simple React state — React.useState with spread operators or Immer handles most cases without Immutable.js overhead
- • Projects requiring native JavaScript object/array compatibility — Immutable.js structures are not plain JS objects; toJS() conversions are expensive
- • JSON serialization pipelines — Immutable.js structures require .toJS() before JSON.stringify; not transparent to standard JS
Interface
Authentication
Local library — no authentication required. MIT licensed.
Pricing
MIT licensed. Zero cost.
Agent Metadata
Known Gotchas
- ⚠ Immutable.js structures are NOT plain JS objects — Map() is not {}, List() is not []; must call .toJS() to convert for JSON.stringify or interop with libraries expecting plain objects
- ⚠ Value equality uses .equals() not ===: immutableMap1.equals(immutableMap2) — === checks reference, not value; easy source of bugs comparing two different Immutable objects with same data
- ⚠ getIn() and setIn() use Immutable.js path arrays: map.getIn(['user', 'address', 'city']) — not dot notation; different from lodash get(obj, 'user.address.city')
- ⚠ Immer has largely replaced Immutable.js for Redux use — Immer works with plain JS objects and lets you write mutating code; Redux Toolkit uses Immer by default
- ⚠ Conversion costs: frequent .toJS() calls negate performance benefits — if you're converting to plain JS frequently, reconsider using Immutable.js
- ⚠ Record types provide fixed schemas: const UserRecord = Record({ name: '', age: 0 }) — useful for typed domain objects but requires upfront schema definition
Alternatives
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Scores are editorial opinions as of 2026-03-06.