I’d like to write simple code on JS but the Visual Studio (why, my god why?) show every line error.
Example:
#pragma strict
var i:int;
Fist line, invalid character, var i: the : character invalid etc…etc…etc…
If I run the game the script work.
The c# code editor work perfect but I’d like programming in JS, and not in NotePad 
Technically Unity does UnityScript, not JavaScript. It’s very, very similar but not exact. Visual Studio isn’t going to like some of the UnityScript syntax and will give you the errors. Everything still compiles though.
If you go into the menu under Tools/Options, then Text Editor/JavaScript/General, you can uncheck the Show Syntax Errors checkbox to remove the in-editor syntax checking.
Alternatively you can try switching to the MonoDevelop editor which probably (maybe?) handles UnityScript syntax better.