Welcome to the Javascript SDK forum! This forum is for javascript programmers looking to extend Construct 2 with custom plugins and behaviors.
Javascript SDK documentation
The SDK has its own manual section - you can view the SDK documentation at:
http://www.scirra.com/manual/15/sdk
Please feel free to use this question to ask anything not in the documentation or that you feel you need clarification for.
Please test with the minifier
One of the most common problems third party plugins and behaviors have is they are broken by the minifier. This is Google Closure Compiler working in ADVANCED_OPTIMIZATIONS mode. Please see this thread for more details. Before publishing your plugin or behavior, please export it with 'Minify script' enabled and upload it to a server to check it still works.