Typo in section "Functions" paragraph "Functions should only be one level of abstraction"

Hi!

I've spotted typo in section "Functions" paragraph "Functions should only be one level of abstraction" in point "Good". It's saying:

class BetterJSAlternative
{
    private string _tokenizer;
    private string _lexer;
    // ...

But both _tokenizer and _lexer are supposed to be classes Tokenizer and Lexer respectively. So it should be something like:

class BetterJSAlternative
{
    private Tokenizer _tokenizer;
    private Lexer _lexer;
    // ...