How to create random generator on HTML5?

Greetings.

I have 5 webpages with games. I want another html5 page to generate 5 random numbers where every number opens one of the game pages.

I used to do this on flash with a simple small .swf and embed it in the HTML page.

It looks like:

variable=random(5);

if variable == 1 {open game page 1};

if variable == 2 {open game page 2};

ans so on..

Now I need to do that with clean HTML5, How to do it?