套件： node-immutable (3.8.2+dfsg-3)

Immutable Data Collections

Immutable data cannot be changed once created, leading to much simpler application development, no defensive copying, and enabling advanced memoization and change detection techniques with simple logic. Persistent data presents a mutative API which does not update the data in-place, but instead always yields new updated data.

Immutable.js provides many Persistent Immutable data structures including: List, Stack, Map, OrderedMap, Set, OrderedSet and Record.

These data structures are highly efficient on modern JavaScript VMs by using structural sharing via [hash maps tries][] and [vector tries][] as popularized by Clojure and Scala, minimizing the need to copy or cache data.

Immutable also provides a lazy Seq, allowing efficient chaining of collection methods like map and filter without creating intermediate representations. Create some Seq with Range and Repeat.

Node.js is an event-based server-side JavaScript engine.