I'm just reading up in the Squiz User Guide and trying to figure out what the Javascript API does. What I 'think' I understand is that you can use this type of asset to access some APIs behind the Squiz Matrix system so you may be able to GET/PUSH content/functionality between a Squiz Matrix website and another non Squiz Matrix website?
I hope I am right. If anyone can quickly illustrate a use case scenario it would be more clear. What I think the asset does not do is allow us to easily access a third party API (preferably through AJAX/JSON) and get the content into a page asset. Currently I just hand code all this stuff in custom JS within a body copy div (or in a design file if its a sitewide thing).