In fact, those libraries exist for some time already and propose rich functions that could be reused directly instead of having to write them in another language, test, debug, and maintain. So in short, people who are used to a js library will hardly want to learn a new language that will bring them troubles and hand work.
The issue with raw Js libraries is that you have to write your own js code to use them, and if you have complex tasks, you can find your self solving browser incompatibility problems, dealing with the js development tools that are limited since it's a script and there are too few assumptions the tools can make for you.
Because of that need, and because dart is a well thought language "that needs fewer lines to say the same things". Projects like AngularDart will inevitably emerge for the most active existing Js libraries.
More complex js "plaforms" will have to adapt: The more the platform was bringing services, the more it will have to do gymnastics to delegate some services to dart or parts of services.
Some blog posts still compare dart with js technologies like this interesting comparative table but this hard choice to do -especially if you have to learn a new language- cannot be left as a statu quo, there are too many things to win in joining instead of competing those technologies.
I'm sure the direction it is taking is not a concurrence but answers to real life problems like "How could I bring that feature to my project without being hardly tied to the library"
We will soon see a competition on who will adapt the first to dart, because dart is still making announcements for new js libraries that become compatible with it, it will fast become a sort of marketplace for new "club members". Especially because js libraries were needed for a long time, and many hundreds of js libraries emerged during that long long period, today if you search for a ready js gallery, you will find a plethora of solutions, some more buggy than others, if you have any kind of need, there are chances you will find your solution already working and tested on the web.
Dart will be the next way for these js libraries that are already in competition to become "visible" on the web, that's why the article says it's becoming an ambassador. I think it is not a good idea to create a "Dart play" website since Dart will surely be there at the right time, but on this specific point I could be wrong, and even this statement could influence the course of things: if some referee website will be born before, maybe they could also be then "bought" by dart with their already existing public...
Do you think I forgot an aspect of the js development world seen by dart aware developers? your comments will be welcome...
