You're doing Option.1 in wrong way. You were sending only control id to javascript function. I think you're creating object there to get value from textbox after matching the element. That's why the slow.
Here better way(than existing one). I'm just getting the value & sending to javascript function.
txtbx1.attributes.add("onclick","Getvalues('" + txtbx1.Text + "')");
One more suggestion(alternative).
Go with jQuery instead of javascript. Using
Click()[
^] event you could reduce the code.