I need a special unique booking ID, which is easy for costumer to read-out over the phone.

It should be 5 characters long, and only use these letters:

```
var letters = "ABCDEFGHJKMNPQRSTUXY";

```

I found this function on stackoverflow but is having a hard time to get it to take chars from my letters and limit itself to 5 chars. 

```
var uniqueId = function() {
  return Math.random().toString(36).substr(2, 16);
};

```

Any help would be appreciated :-)