Passing ASP.NET Server control id to Java script function

I’m recently working on a web application, that invovles creating a Date Picker Control. I’ve decided to leverage calendar javascript and develop them as the textox and an image invoking Calendar Javascript.

My datepicker control looks like the following

Here i’m trying to pass the id of textbox control to the javascript. Javascript could not recognize that.

I’ve learnt that the way to do is as follows