What js framework should I use to create a website builder that has drag and drop, wysiwyg and generates code like visual basic? [on hold]

I am trying to develop a website builder where you could just drop elements like buttons and modify their properties ( pretty much like what we do with controls on visual basic). Then an autogenerated code will be created which the user can modify. I am having problems on where to start and what frameworks shall I use to make this project easier.