You have been a web developer and you search how to test your JS code in an efficient way? JS BIN is there to lighten you this task.
No need to reinvent the wheel for every development or web project. The web is full of scripts made by guys much smarter than you,which are optimized, take into account all browsers, etc.
These sites are very useful when you want to isolate by sending a piece of code to someone, when you ask a question on a forum for example, or to test a regular expression.
I do not know about you but for my case, the problem is always the same when I am using an already existing piece of code. The provided demo works but when I integrate it with an already existing code it does not work.
So I prefer to isolate the portion of the code and rotate it on online space. This is how I advise these publishers ready for jobs that can be useful.
Experiment codes with jsFiddle
Exam codes with CodePen
Try codes with JS Bin
The idea is to be able to produce in 2 min a script without having to redo the whole structure ( HTML, CSS, js ) and to be able to share it quickly via a direct URL.