Get list item count in Ecma script

var selectedItems = SP.ListOperation.Selection.getSelectedItems();
var ci2 = CountDictionary(selectedItems);

http://msdn.microsoft.com/en-us/sp2010devtrainingcourse_clientobjectmodellab_topic4

Exercise 1: Retrieving Lists

References--Microsoft.SharePoint.Client       Micorosoft.SharePoint.Client.Runtime

C:\Program Files\Common Files\Microsoft Shared\web server extensions\14\ISAPI

C# 1.      private void ShowButton_Click(object sender, EventArgs e) 2.      { 3.              //Show the hourglass wait cursor 4.              this.Cursor = Cursors.WaitCursor; 5.              ListsListBox.Items.Clear(); 6.              //Get a context 7.              using (ClientOM.ClientContext ctx = 8.              new ClientOM.ClientContext(UrlTextBox.Text)) 9.              { 10.                   //Get the site 11.                   ClientOM.Web site = ctx.Web; 12.                   ctx.Load(site); 13.                   //Get Lists 14.                   ctx.Load(site.Lists); 15.                   //Query 16.                   ctx.ExecuteQuery(); 17.                   //Fill List 18.                   foreach (ClientOM.List list in site.Lists) 19.                   { 20.                       ListsListBox.Items.Add(list.Title); 21.                   } 22.                   //Return the cursor to normal 23.                   this.Cursor = Cursors.Default; 24.           } 25.   }

VB.NET Private Sub ShowButton_Click(ByVal sender As Object, ByVal e As EventArgs)         Handles ShowButton.Click         'Show the hourglass wait cursor         Me.Cursor = Cursors.WaitCursor         ListsListBox.Items.Clear()         'Get a context         Using ctx As New ClientOM.ClientContext(UrlTextBox.Text)             'Get the site             Dim site As ClientOM.Web = ctx.Web             ctx.Load(site)             'Get Lists             ctx.Load(site.Lists)             'Query             ctx.ExecuteQuery()             'Fill List             For Each list As ClientOM.List In site.Lists                 ListsListBox.Items.Add(list.Title)             Next             'Return the cursor to normal             Me.Cursor = Cursors.[Default]         End Using     End Sub