Basic error management (syntax and illegal characters).
Correction of errors display
Comment management and lexing of ";" and ",".
Lexing of comparison operators.
Lexing of "!" and ".".
Lexing of arithmetical operators (+ - * / %).
Lexing of boolean operators (&& and ||).
Lexing of control keywords (if, else, in).
Lexing of object keywords (this, null, new, instanceof).
Boolean management.