Collection iteration more similar to Map.

packages/xo-collection/src/collection.js

@@ -163,6 +163,22 @@ export default class Collection extends EventEmitter {
   * [Symbol.iterator] () {
     const {_items: items} = this
 
+    for (let key in items) {
+      yield [key, items[key]]
+    }
+  }
+
+  * keys () {
+    const {_items: items} = this
+
+    for (let key in items) {
+      yield key
+    }
+  }
+
+  * values () {
+    const {_items: items} = this
+
     for (let key in items) {
       yield items[key]
     }

packages/xo-collection/src/collection.spec.js

@@ -39,8 +39,26 @@ describe('Collection', function () {
   it('is iterable', function () {
     const iterator = this.col[Symbol.iterator]()
 
+    expect(iterator.next()).to.eql({done: false, value: ['bar', 0]})
+    expect(iterator.next()).to.eql({done: true, value: undefined})
+  })
+
+  describe('#keys()', function () {
+    it('returns an iterator over the keys', function () {
+    const iterator = this.col.keys()
+
+    expect(iterator.next()).to.eql({done: false, value: 'bar'})
+    expect(iterator.next()).to.eql({done: true, value: undefined})
+    })
+  })
+
+  describe('#values()', function () {
+    it('returns an iterator over the values', function () {
+    const iterator = this.col.values()
+
     expect(iterator.next()).to.eql({done: false, value: 0})
     expect(iterator.next()).to.eql({done: true, value: undefined})
+    })
   })
 
   describe('#add()', function () {