Polymorphism in JavaScript

I am a senior software Consultant and have been working in IT for the past 6 years.
I started as a junior web developer back in 2006 then was promoted to a full developer a year later then a senior developer some years later.
I have held positions as Scrum Master and I am currently working as a software consultant.
Throughout my experience as a web developer, I have spent a lot of time doing both front and back end development.
I have got experience in the following technologies:
ASP.Net 2+, C#, SQL Server 2005+, Java, SilverLight

As far as front-end development is concerned, I am experienced in CSS, JavaScript, XHTML etc...