HTML5/ Javascript support in SUP 2.2- HWC

Could some body please explain the extent of javascript and html5 support in HWC applications in SUP 2.2? I have recently started working out on this technology and some very basic functionalities like passing variables between JS functions do not seem to work.

For example:

1. If I have something like:

               function fun1(){var x=1; fun2(x); } //fun2() is another function

      This does not work and the page simply does not load.

2. However, if I pass an instance of object like:

               function fun1(){ fun2(this);}

     This works fine.

I could not understand why this happens...