How to get User Control value using Javascript in an .aspx file

Hello,

I have a aspx file that include a user control file. I need to get the textbox value that is in the user control page (user.ascx file) using javascript in the mypage.aspx file. Here is my code: 

mypage.aspx:

<%@ Register TagPrefix="uc1" TagName="user" Src Go to the complete details ...