diff --git a/js/src/listitem.js b/js/src/listitem.js
index df28216..2f09c8d 100644
--- a/js/src/listitem.js
+++ b/js/src/listitem.js
@@ -18,8 +18,9 @@
  */
 
 /**
- * @property {string} listId
+ * @class uListItem
  * @property {string} listValue
+ * @property {string} listText
  */
 export default class uListItem {
   /**
@@ -30,4 +31,11 @@ export default class uListItem {
     this.listValue = String(id);
     this.listText = String(value);
   }
+
+  /**
+   * @return {string}
+   */
+  toString() {
+    return `[${this.listValue}, ${this.listText}]`;
+  }
 }
diff --git a/js/src/observe.js b/js/src/observe.js
index 0125fd4..d1feddf 100644
--- a/js/src/observe.js
+++ b/js/src/observe.js
@@ -26,8 +26,8 @@ export default class uObserve {
    * observe(obj, prop, observer) observes given property prop;
    * observe(obj, observer) observes all properties of object obj.
    * @param {Object} obj
-   * @param {(string|function)} p1
-   * @param {function=} p2
+   * @param {(string|ObserveCallback)} p1
+   * @param {ObserveCallback=} p2
    */
   static observe(obj, p1, p2) {
     if (typeof p2 === 'function') {
@@ -47,7 +47,7 @@ export default class uObserve {
    * Observe object's proporty. On change call observer
    * @param {Object} obj
    * @param {?string} property
-   * @param {function} observer
+   * @param {ObserveCallback} observer
    */
   static observeProperty(obj, property, observer) {
     this.addObserver(obj, observer, property);
@@ -60,6 +60,7 @@ export default class uObserve {
       set: (newValue) => {
         if (obj._values[property] !== newValue) {
           obj._values[property] = newValue;
+          console.log(`${property} = ` + (Array.isArray(newValue) && newValue.length ? `[${newValue[0]}, …](${newValue.length})` : newValue));
           uObserve.notify(obj._observers[property], newValue);
         }
         if (Array.isArray(obj[property])) {
@@ -75,7 +76,7 @@ export default class uObserve {
   /**
    * Recursively add observer to all properties
    * @param {Object} obj
-   * @param {function} observer
+   * @param {ObserveCallback} observer
    */
   static observeRecursive(obj, observer) {
     for (const prop in obj) {
@@ -88,7 +89,7 @@ export default class uObserve {
   /**
    * Observe array
    * @param {Object} arr
-   * @param {function} observer
+   * @param {ObserveCallback} observer
    */
   static observeArray(arr, observer) {
     this.addObserver(arr, observer);
@@ -97,6 +98,7 @@ export default class uObserve {
         const descriptor = Object.getOwnPropertyDescriptor(Array.prototype, operation);
         descriptor.value = function () {
           const result = Array.prototype[operation].apply(arr, arguments);
+          console.log(`[${operation}] ` + arr.length ? `[${arr[0]}, …](${arr.length})` : arr);
           uObserve.notify(arr._observers, arr);
           return result;
         };
@@ -107,7 +109,7 @@ export default class uObserve {
   /**
    * Store observer in object
    * @param {Object} obj Object
-   * @param {function} observer Observer
+   * @param {ObserveCallback} observer Observer
    * @param {string=} property Optional property
    */
   static addObserver(obj, observer, property) {
@@ -130,7 +132,7 @@ export default class uObserve {
 
   /**
    * Notify observers
-   * @param {Set<function>} observers
+   * @param {Set<ObserveCallback>} observers
    * @param {*} value
    */
   static notify(observers, value) {
@@ -140,4 +142,10 @@ export default class uObserve {
       })();
     }
   }
+
+  /**
+   * Notify callback
+   * @callback ObserveCallback
+   * @param {*} value
+   */
 }
diff --git a/js/src/user.js b/js/src/user.js
index d4b2609..19a75b0 100644
--- a/js/src/user.js
+++ b/js/src/user.js
@@ -19,6 +19,7 @@
 
 import uAjax from './ajax.js';
 import uListItem from './listitem.js';
+import uTrack from './track.js';
 
 /**
  * @class uUser
@@ -37,6 +38,13 @@ export default class uUser extends uListItem {
     this.login = login;
   }
 
+  /**
+   * @return {Promise<uTrack, string>}
+   */
+  fetchLastPosition() {
+    return uTrack.fetchLatest(this);
+  }
+
   /**
    * @throws
    * @return {Promise<uUser[], string>}
diff --git a/js/test/user.test.js b/js/test/user.test.js
index b91cda6..9d3f40a 100644
--- a/js/test/user.test.js
+++ b/js/test/user.test.js
@@ -17,6 +17,7 @@
  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
+import uTrack from '../src/track.js';
 import uUser from '../src/user.js';
 
 describe('User tests', () => {
@@ -33,6 +34,28 @@ describe('User tests', () => {
       expect(user.id).toBe(id);
       expect(user.login).toBe(login);
     });
+
+    it('should call uTrack.fetchLatest method', () => {
+      // given
+      const id = 1;
+      const login = 'test';
+      const user = new uUser(id, login);
+      spyOn(uTrack, 'fetchLatest');
+      // when
+      user.fetchLastPosition();
+      // then
+      expect(uTrack.fetchLatest).toHaveBeenCalledWith(user);
+    });
+
+    it('should get class string representation', () => {
+      // given
+      const id = 1;
+      const login = 'test';
+      // when
+      const user = new uUser(id, login);
+      // then
+      expect(user.toString()).toBe(`[${id}, ${login}]`);
+    });
   });
 
   describe('ajax tests', () => {
@@ -58,5 +81,6 @@ describe('User tests', () => {
         })
         .catch(() => done.fail('reject callback called'));
     });
+
   });
 });