ref #5 Use native Map. Store id in the decoration object

lib/text-decoration-collection.js

@@ -1,40 +1,35 @@
 
-const _ = require('lodash');
-
 class TextDecorationCollection {
 
     constructor({generateUuid}) {
         this._generateUuid = generateUuid;
 
-        this._map = Object.create(null);
+        this._map = new Map();
     }
 
     add({pattern, colour, decorationType}) {
         const id = this._generateUuid();
-        const decoration = {pattern, colour, decorationType};
-        this._map[id] = decoration;
-        return Object.assign({id}, decoration);
+        const decoration = {id, pattern, colour, decorationType};
+        this._map.set(id, decoration);
+        return decoration;
     }
 
     get(id) {
-        const value = this._map[id];
-        return value ? Object.assign({id}, value) : null;
+        return this._map.get(id);
     }
 
     remove(id) {
-        this._map[id] = null;
+        this._map.delete(id);
     }
 
     find(predicate) {
-        const id = _.findKey(this._map, decoration => decoration && predicate(decoration));
-        return id ? Object.assign({id}, this._map[id]) : null;
+        return Array.from(this._map.values())
+            .find(decoration => predicate(decoration)) || null;
     }
 
     toList() {
-        return _.reduce(this._map,
-            (result, value, key) => value ? [...result, Object.assign({id: key}, value)] : result,
-            []
-        );
+        return Array.from(this._map.values())
+            .reduce((result, decoration) => [...result, decoration], []);
     }
 
 }