Immutable.js persistent data structures.

immutable-js-demo.js

// Use in place of `[]`.
const list1 = Immutable.List(['A', 'B', 'C']);
const list2 = list1.push('D', 'E');

console.log([...list1]); // ['A', 'B', 'C']
console.log([...list2]); // ['A', 'B', 'C', 'D', 'E']


// Use in place of `new Map()`
const map1 = Immutable.Map([
  ['one', 1],
  ['two', 2],
  ['three', 3]
]);
const map2 = map1.set('four', 4);

console.log([...map1]); // [['one', 1], ['two', 2], ['three', 3]]
console.log([...map2]); // [['one', 1], ['two', 2], ['three', 3], ['four', 4]]


// Use in place of `new Set()`
const set1 = Immutable.Set([1, 2, 3, 3, 3, 3, 3, 4]);
const set2 = set1.add(5);

console.log([...set1]); // [1, 2, 3, 4]
console.log([...set2]); // [1, 2, 3, 4, 5]