Converting a huge ActionScript 3 project to HTML5 and JS

Hello,

I have a huge project with dozens of packages and hundreds of classes written in Action Script 3. The main Flash document just takes a main class Sample.as and compile the project into a single SWF file. How can I convert all of the code into a HTML5 and JS codebase? What will be lost? What other steps need to be done to have a similar project running on HTML5 and JS? Thank you.