How to handle warnings for proprietary/custom properties of built-in objects in TypeScript

Question

I am using Personas which relies on the proprietary property navigator.id. Since this property is not standard, the TypeScript compiler generates the following warning:

Answer 1

Add checks like if(navigator.id != null && typeof navigator.id != 'undefined') before stmt where navigator.id is referred

Answer 2

1) You can reinterpret navigator prop.

(<any>navigator).id.request();

2) You can declare id prop youself

mycompany.lib.d.ts

interface Navigator {
  id: any
}

app.ts

navigator.id.request();

see this video http://channel9.msdn.com/posts/Anders-Hejlsberg-Introducing-TypeScript/ There Anders tell as jQuery.UI add new methods to jQuery (see 46 min)