Add `instance.group` back instead of changing the option object

dist/shuffle.js

@@ -160,7 +160,7 @@ return /******/ (function(modules) { // webpackBootstrap
 	
 	    this.useSizer = false;
 	    this.lastSort = {};
-	    this.lastFilter = Shuffle.ALL_ITEMS;
+	    this.group = this.lastFilter = Shuffle.ALL_ITEMS;
 	    this.isEnabled = true;
 	    this.isDestroyed = false;
 	    this.isInitialized = false;
@@ -312,7 +312,7 @@ return /******/ (function(modules) { // webpackBootstrap
 	      // This is saved mainly because providing a filter function (like searching)
 	      // will overwrite the `lastFilter` property every time its called.
 	      if (typeof category === 'string') {
-	        this.options.group = category;
+	        this.group = category;
 	      }
 	
 	      return set;

js/demos/homepage.js

@@ -167,10 +167,10 @@ Demo.prototype._handleSearchKeyup = function (evt) {
   this.shuffle.filter(function (element, shuffle) {
 
     // If there is a current filter applied, ignore elements that don't match it.
-    if (shuffle.options.group !== Shuffle.ALL_ITEMS) {
+    if (shuffle.group !== Shuffle.ALL_ITEMS) {
       // Get the item's groups.
       var groups = JSON.parse(element.getAttribute('data-groups'));
-      var isElementInCurrentGroup = groups.indexOf(shuffle.options.group) !== -1;
+      var isElementInCurrentGroup = groups.indexOf(shuffle.group) !== -1;
 
       // Only search elements in the current group
       if (!isElementInCurrentGroup) {

src/shuffle.js

@@ -49,7 +49,7 @@ class Shuffle {
 
     this.useSizer = false;
     this.lastSort = {};
-    this.lastFilter = Shuffle.ALL_ITEMS;
+    this.group = this.lastFilter = Shuffle.ALL_ITEMS;
     this.isEnabled = true;
     this.isDestroyed = false;
     this.isInitialized = false;
@@ -186,7 +186,7 @@ class Shuffle {
     // This is saved mainly because providing a filter function (like searching)
     // will overwrite the `lastFilter` property every time its called.
     if (typeof category === 'string') {
-      this.options.group = category;
+      this.group = category;
     }
 
     return set;