Its because at the very end there are non letters that they expect us to deal with. I believe its a string of "-.-"

What happens to empty_return if you call nato twice? Try console.log(nato("a")); console.log(nato("b")). What's the expected output? What's your output? If you can answer all those questions, you should be able to fix your problem. Also, please use code blocks to post code. Either ``` backticks:

```javascript
function helloWorld(){
  return "Hello, world!";
}
```

Or indent your code by 4 spaces.

    function helloWorld(){
      return "Hello, world!";
    }

Good luck.

????

Ahem ;). That being said, you should provide more information. Which language, and what's your solution (mark as having spoiler content!)?

'Lambda' refers to either a keyword in some languages or an actual construct. In javascript, there are no 'lambdas', just functions in lambda-calculus-like format. Therefore, no.

You should always add both the code and the language. Otherwise one cannot help you. (Don't forget to mark your post as spoiler)