Which method/event can pop up the "Save For Web" dialog as well as getting the export file path from the returning result

Could anyone please point me out with which method/event I could use to trigger the “Save for web” dialog as well as getting the file path from the returning results.

basically, I need the sample code which can pop up the "Save For Web" dialog automatically for the current user by a button click on a HTML5 illustrator extension.

Then user can make some configuration then save the file somewhere in the disk. Then the programming needs to get the path which user saved the file and continue with some other tasks.

Thank you very much!