add rename() to Mappable

README.md

@@ -964,6 +964,16 @@ given.map({ strings: 2, numbers: 1, functions: 4 })
   .keys() // ['numbers', 'functions', 'strings']
 ```
 
+### rename
+
+Renames the given key with the new key if found, keeping the original insertion order.
+
+```javascript
+given.map({ one: 1, to: 2, three: 3 })
+  .rename('to', 'two')
+  .keys() // ['one', 'two', 'three']
+```
+
 ## Numbers
 
 <small>

src/objects/Mappable.ts

@@ -54,6 +54,15 @@ class Mappable<K = any, V = any> extends Map<K, V> {
       .toMap()
   }
 
+  /**
+   * Renames the given key with the new key if found, keeping the original insertion order.
+   */
+  rename(oldKey: K, newKey: K) {
+    return this.mapKeys((_, key) => {
+      return (key === oldKey) ? newKey : key
+    })
+  }
+
   /**
    * Iterates the entries through the given callback and assigns each result as the value.
    */

test/mappable.spec.js

@@ -70,4 +70,12 @@ test('only() returns a new map with only the given keys', assert => {
 test('except() returns a new map with all keys except for the given keys', assert => {
   const map = given.map({ one: 1, two: 2, three: 3 }).except(['one', 'two'])
   assert.deepEqual(map.keys(), ['three'])
+})
+
+test('rename() renames a key if found', assert => {
+  const map = given.map({ one: 1, to: 2, three: 3 }).rename('to', 'two')
+  assert.deepEqual(map.keys(), ['one', 'two', 'three'])
+
+  const map2 = given.map({ one: 1, two: 2, three: 3 }).rename('for', 'four')
+  assert.deepEqual(map2.keys(), ['one', 'two', 'three'])
 })