Javascript How to get SelectedText from Asp Dropdownlist or HTML Select option

asp:DropDownList is the server side control of asp.net & the drop down selection list is an element of HTML forms commonly know as Combo Box. Most of the times developers need to find or get the Selected Index value, Selected Value & Selected Text. In this post i will show you how one can write a cross-browser supported client side javascript to get Selected Index, Selected Text & Selected Value