No suggestions for different methods and properties pop up, like they do in the Eclipse IDE and Flash Builder IDE. Like when you press dot after object, it shows all the methods and properties relating to that object and it becomes really easy to see what the parameters are and needed to be passed and stuff.

This isn't really my cup of tea, but I'm sure there are Eclipse plugins that can do this to some extent for JavaScript. Due to the nature of functions and the object model in JavaScript, it would be much harder to do this for all cases than a language like Java.

How to organize code? In ActionScript3, I could simply make different classes in different packages. I could then import and use those classes in one main file. How does it work in JavaScript?

Check out RequireJS. As far as I know, it's the most commonly accepted method for formatting JavaScript "modules" (which are a JavaScript idiom).

Functions. I have seen people use anonymous functions in javascript. But I am compelled to write external functions as I am in the habit of it. What is better in JavaScript workflow? What do you advice?

You can write a lot of JavaScript without having to resort to anonymous functions, but anonymous functions make it easier. I think this is something that you can learn in time.

How is code executed within a HTML file? So if I have several tags and I declare a variable in one of them, can the tags below it and above it access that variable?

Yes, the tags below it will have access to that variable. Code is executed linearly, and JavaScript's scoping is simple, limited, and oft criticized (but efficient if you know the caveats).

No suggestions for different methods and properties pop up, like they do in the Eclipse IDE and Flash Builder IDE. Like when you press dot after object, it shows all the methods and properties relating to that object and it becomes really easy to see what the parameters are and needed to be passed and stuff.

This isn't really my cup of tea, but I'm sure there are Eclipse plugins that can do this to some extent for JavaScript. Due to the nature of functions and the object model in JavaScript, it would be much harder to do this for all cases than a language like Java.

How to organize code? In ActionScript3, I could simply make different classes in different packages. I could then import and use those classes in one main file. How does it work in JavaScript?

Check out RequireJS. As far as I know, it's the most commonly accepted method for formatting JavaScript "modules" (which are a JavaScript idiom).

Functions. I have seen people use anonymous functions in javascript. But I am compelled to write external functions as I am in the habit of it. What is better in JavaScript workflow? What do you advice?

You can write a lot of JavaScript without having to resort to anonymous functions, but anonymous functions make it easier. I think this is something that you can learn in time.

How is code executed within a HTML file? So if I have several tags and I declare a variable in one of them, can the tags below it and above it access that variable?

The tags below it will have access to that variable. Code is executed linearly, and JavaScript's scoping is simple, limited, and oft criticized (but efficient if you know the caveats).