Javascript intellisense was not working in visual studio environment. The project already had a reference to ajaxcontroltoolkit, after searching on web for nearly an hour I got below walkthrough by microsoft which works like miracle :) Wish they had added this intellisense by default, after all I just wanted to see simple dom objects like document.getElementById()

Add reference to ajaxcontrol toolkit to your project and add below code at top of the page

<asp:ScriptManager ID="ScriptManager1" runat="server">
  <Scripts>
    <asp:ScriptReference Path="JScript.js" />
  </Scripts>
</asp:ScriptManager>

Also, to automatically complete highlighted word in intellisense uncheck Tools -> Options -> Text Editor -> JScript -> Miscellaneous -> Only use tab or enter to commit.


Reference: http://msdn.microsoft.com/en-us/library/vstudio/bb385674(v=vs.100).aspx