ASP.Net: Add (Insert) Items (Options) to DropDownList on Button click using JavaScript

Here Mudassar Ahmed Khan has explained with an example, how to dynamically add (insert) Items (Options) to ASP.Net DropDownList on Button Click using JavaScript. The Items (Options) Text and Value parts will be dynamically fetched from TextBoxes and then the Items (Options) will be added to ASP.Net DropDownList using plain JavaScript.