Do you mean you only want a match if the pattern matches the whole string not just part of it?

You do that by anchoring the pattern to the beginning and end /^\+\d\d\d\d\d\d$/.

Note that the $ anchor actually permits a newline at the end of the string. If this bothers you then use \Z instead.

As others have pointed out /^\+\d\d\d\d\d\d$/ is probably more tidy as /^\+\d{6}$/.

(Oh, and BTW there was a spurious 's' in your OP - you should probably go update it.)