immutable-js: add

immutable-js.md

@@ -0,0 +1,43 @@
+---
+title: Immutable.js
+---
+
+```js
+var Immutable = require('immutable')
+```
+
+## Maps
+
+```js
+var map = Immutable.Map({ a: 1, b: 2, c: 3 })
+
+map
+  .set('b', 50)
+  .get('b') // 50
+```
+
+## Lists
+
+```js
+var list = Immutable.List.of(1, 2)
+
+list
+  .push(3, 4, 5)
+  .unshift(0)
+  .concat(list2, list3)
+  .get(0)
+  .size
+```
+
+## Nested maps
+
+```js
+var nested = Immutable.fromJS({ user: { profile: { name: 'John' } } })
+
+nested
+  .mergeDeep({ user: { profile: { age: 90 } } })
+  .setIn([ 'user', 'profile', 'name' ], 'Jack')
+  .updateIn([ 'user', 'profile', 'name' ], (s) => s.toUpperCase())
+  .getIn(['user', 'profile', 'name']) // 'Jack'
+```
+