Try adding a backslash:

var unrealisticPhoneNumberRegex = /^[a-zA-Z0-9-().s]{10,15}$/;

Now it's still not very useful because you allow an arbitrary number of punctuation characters too. Really, validating a phone number like this — especially if you want it to really work for all possible international phone numbers — is probably a hopeless task. I suggest you go with what @BalusC suggests.