Add isEmpty function to ItemList (#1218)

* Add isEmpty function to ItemList

* Fix coding style to be consistent.

* Recompiled app.js for both js/admin/ and js/forum/

framework/core/js/admin/dist/app.js

@@ -23425,14 +23425,25 @@ System.register("flarum/utils/ItemList", [], function (_export, _context) {
         }
 
         /**
-         * Check whether an item is present in the list.
+         * Check whether the list is empty.
          *
-         * @param key
          * @returns {boolean}
+         * @public
          */
 
 
         babelHelpers.createClass(ItemList, [{
+          key: "isEmpty",
+          value: function isEmpty() {
+            for (var i in this.items) {
+              if (this.items.hasOwnProperty(i)) {
+                return false;
+              }
+            }
+
+            return true;
+          }
+        }, {
           key: "has",
           value: function has(key) {
             return !!this.items[key];

framework/core/js/forum/dist/app.js

@@ -31837,14 +31837,25 @@ System.register("flarum/utils/ItemList", [], function (_export, _context) {
         }
 
         /**
-         * Check whether an item is present in the list.
+         * Check whether the list is empty.
          *
-         * @param key
          * @returns {boolean}
+         * @public
          */
 
 
         babelHelpers.createClass(ItemList, [{
+          key: "isEmpty",
+          value: function isEmpty() {
+            for (var i in this.items) {
+              if (this.items.hasOwnProperty(i)) {
+                return false;
+              }
+            }
+
+            return true;
+          }
+        }, {
           key: "has",
           value: function has(key) {
             return !!this.items[key];

framework/core/js/lib/utils/ItemList.js

@@ -20,6 +20,22 @@ export default class ItemList {
     this.items = {};
   }
 
+  /**
+   * Check whether the list is empty.
+   *
+   * @returns {boolean}
+   * @public
+   */
+  isEmpty() {
+    for (const i in this.items) {
+      if(this.items.hasOwnProperty(i)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
   /**
    * Check whether an item is present in the list.
    *